Search

While cross‐species comparisons of birds suggest that as latitude decreases or elevation increases, clutch size decreases and the duration of developmental stages and parental attentiveness increases, studies comparing populations of the same species are rare. We studied populations of house wrens, Troglodytes aedon, at high and low elevations in California and Costa Rica, collecting data on clutch size, the duration of incubation and nestling periods, parental attentiveness, nestling growth rate, and nesting success. Our data support results from cross‐species comparisons, but also revealed unanticipated results from low elevation temperate zone house wrens in the southwest. This population had prolonged incubation and nestling periods similar to those found in the tropics. We also found that temperate zone females, especially those at our higher elevation site, spent more of their day incubating than did tropical females. Nest temperature at our high elevation temperate zone site was higher than that at all other tropical sites. Age at fledging did not differ between sites. Total feeding rates per chick and male feedings per chick did not vary between sites. Nest success rates showed the predicted effect of latitude, but not the predicted effects of elevation. Our results extend low elevation house wren research into the southwestern US and contribute the first intraspecific elevational comparison in the Neotropics. Data from our low elevation southwestern site present a unique suite of life history traits that align more with tropical house wrens, although with a larger clutch size, and point to food limitation and/or high predation pressure as being possible drivers of some of these differences. These results highlight the need for additional studies of house wrens and other broadly distributed species at a more diverse array of sites to better understand which forces drive the evolution of different life history strategies across major biogeographical gradients. [ABSTRACT FROM AUTHOR]

Larvae of the federally threatened Euproserpinus euterpe from Walker Basin, Kern Co., CA. and Carrizo Plains, San Luis Obispo Co., CA populations were reared to the pupal and adult stage for the first time. The E. euterpe pupa is described. Mature larvae excavated a subterranean pupal chamber in an unusual (not burrowing solely headfirst) manner, but typical of other species in the sphingid tribe, Macroglossini. Soil depth of pupation ranged from 5 to 11 cm, mean = of 7.14±1.83 cm s.d. cm (n=14) for the Walker Basin population. Pupae were maintained in artificial pupal cells, facilitating observations of development. Multiple-year diapause to three years, predicted based on field observations, was demonstrated in the laboratory. Soil humidity during the fall and winter season appears critical to break pupal diapause. Pupae did not travel through the soil. Adults burrowed to the soil surface after eclosion from the pupa. The wing expansion behavior of adults at the soil surface, along with their vertical, upward wing expansion, are described. [ABSTRACT FROM AUTHOR]

Offspring size is a key functional trait that can affect subsequent life history stages; in many species, it exhibits both local adaptation and phenotypic plasticity. Variation among populations in offspring size may be explained by various factors, including local climatic conditions. However, geographic variation in climate may be partitioned into long‐term and interannual sources of variation, which may differ in their effects on population mean offspring size. To assess environmental correlates of offspring size, we evaluated geographic variation in seed mass among 88 populations representing 6 species of Streptanthus (Brassicaceae) distributed across a broad climatic gradient in California. We examined the effects of temperature‐mediated growing season length and precipitation on population mean seed mass to determine whether it is best explained by (1) long‐term mean climatic conditions; (2) interannual climate anomalies (i.e., deviations in climate from long‐term means) during the year of seed development, or (3) interactions between climate variables. Both long‐term mean climate and climate anomalies in the year of collection were associated with population mean seed mass, but their effects differed in direction and magnitude. Relatively large seeds were produced at chronically wet sites but also during drier‐than‐average years. This contrast indicates that these associations may be generated by different mechanisms (i.e., adaptive evolution vs. phenotypic plasticity) and may be evidence of countergradient plasticity in seed mass. In addition, populations occurring in locations characterized by relatively long growing seasons produced comparatively large seeds, particularly among chronically dry sites. This study highlights the need to consider that the responses of seed mass to long‐term versus recent climatic conditions may differ and that climate variables may interact to predict seed mass. Such considerations are especially important when using these patterns to forecast the long‐ and short‐term responses of seed mass to climate change. The results presented here also contribute to our broader understanding of how climate drives long‐term (e.g., local adaptation) and short‐term (e.g., phenotypic plasticity) variation in functional traits, such as offspring size across landscapes. [ABSTRACT FROM AUTHOR]

Intentional introductions of non-native fishes can severely affect native communities. Wakasagi (Hypomesus nipponensis, referred to as Japanese Pond Smelt) are native to Japan and were once separated from their non-native congener the endangered Delta Smelt (Hypomesus transpacificus) of the San Francisco Estuary (hereon "estuary") of California. Wakasagi were introduced into California reservoirs in the 20th century as forage fish. Wakasagi have since expanded their distribution downstream to the estuary, but less is known about Wakasagi's current distribution status, biology in the estuary, and negative influences on Delta Smelt. In this study, we took a comparative approach by synthesizing long-term field monitoring surveys, modeling environmental associations, and quantifying phenology, growth, and diets of Wakasagi and Delta Smelt to describe abundance and range, trends of co-occurrence, and shared ecological roles between smelt species. We found Wakasagi in greatest abundance in the upper watershed below source reservoirs, and in the northern regions of the estuary with the most co-occurrence with Delta Smelt; however, their range extends to western regions of the estuary, and we found evidence of an established population that annually spawns and rears in the estuary. We found these smelt species have similar ecological roles demonstrated by overlaps in habitat use (e.g., an association with higher turbidities and higher outflow), phenology, growth, and diets. Despite similarities, earlier hatching and rearing of Wakasagi during cooler months and reduced growth during warmer drought years suggest this species is unlike typical non-natives (e.g., Centrarchids), and they exhibit a similar sensitivity to environmental variability as Delta Smelt. This sensitivity may be why Wakasagi abundance remains relatively low in the estuary. [ABSTRACT FROM AUTHOR]

Steelhead (Oncorhynchus mykiss expressing an anadromous life history) in the Sacramento and San Joaquin rivers and their tributaries in California's Central Valley (CCV) belong to a Distinct Population Segment (DPS) that is listed as threatened under the US Endangered Species Act. Although contemporary management and recovery plans include numerous planned and ongoing efforts seeking to aid in DPS recovery--such as gravel augmentation, manipulation of spring flows, and restoration of rearing and spawning habitat--a paucity of data precludes the possibility of evaluating the effect of these actions on populations of Steelhead in CCV streams. Knowledge gaps relating to historic and current abundance, population-specific ratios of resident and anadromous life-history expression, and the influence of hatchery-reared fish remain largely unaddressed. This is partly a result of aspects of Steelhead biology that make them difficult to monitor, including the multitude of factors that contribute to the expression of anadromy, polymorphic populations, and migration periods that coincide with challenging field conditions. However, these gaps in understanding are also partly the result of an institutional focus on Chinook Salmon (Oncorhynchus tshawytscha) and a pervasive notion that actions benefiting Chinook populations will also benefit Steelhead populations. To evaluate these gaps and to suggest approaches for assessing DPS recovery actions, we review available data and existing monitoring efforts, and consider the actions necessary to inform the development of targeted O. mykiss monitoring programs. Current management and recovery goals focus on abundance estimates of Steelhead only, yet current monitoring is insufficient for reliable estimates. We argue that a reallocation of monitoring resources to better understand the interaction between resident O. mykiss and Steelhead would provide better data to estimate the vital rates needed to evaluate the effects of recovery actions. [ABSTRACT FROM AUTHOR]

We document for the first time the larval food plants of Anoncia mosa Hodges (Cosmopterigidae) mining the leaves of Collinsia heterophylla and C. tinctoria (Lamiales: Plantaginaceae) in Madera County, California. We describe and illustrate the mine, larval feeding habits, last instar larva and pupa of Anoncia mosa, then compare the immature stages to other Cosmopterigidae to help identify this species and call attention to some overlooked morphological characters. These include the larval P seta, larval cuticular texture and the genital opening of the pupa in a pit. We partially describe the previously unknown pupa of Euclemensia. We also use characters of the immature stages to briefly discuss the systematic placement of three taxa. The family status of the Chrysopeleiidae and the inclusion of Triclonella in the Cosmopterigidae are supported by the pupa but not the larva. Conversely, the systematic placement of Metharmostis in Cosmopterigidae is better supported by the larva than the pupa. Our study is an example of the need to save larval and pupal exuviae for morphological descriptions. [ABSTRACT FROM AUTHOR]

To inform management and conservation of the species, we investigated the distribution of anadromy and residency of steelhead/rainbow trout (Oncorhynchus mykiss) in the Eel River of northwestern California. We determined maternal anadromy versus residency for 106 juvenile O. mykiss using otolith microchemistry. To attempt to relate patterns of anadromy with environmental factors known to influence its distribution in O. mykiss in other places, fish were collected from 52 sites throughout the drainage covering a range of stream size (0.1–7.7 m3 /s estimated mean annual run-off) and distance from the ocean (23–219 km). Sixty-one of 91 fish sampled below prospective barriers had anadromous mothers, while 1 of 15 fish sampled above barriers had an anadromous mother. We did not detect any influence of stream size or distance from the ocean on the occurrence of anadromy. Fish with resident mothers were found at 21 of 46 sites below barriers. The current broad distribution of fish with resident mothers indicates the importance of maintaining freshwater conditions suitable for resident adults and juveniles age-1 and older, such as preserving dry-season stream flows. [ABSTRACT FROM AUTHOR]

The densities of highly competent plant hosts (i.e. those that are susceptible to and successfully transmit a pathogen) may shape pathogen community composition and disease severity, altering disease risk and impacts. Life history and evolutionary history can influence host competence; longer lived species tend to be better defended than shorter lived species and pathogens adapt to infect species with which they have longer evolutionary histories. It is unclear, however, how the densities of species that differ in competence due to life and evolutionary histories affect plant pathogen community composition and disease severity.We examined foliar fungal pathogens of two host groups in a California grassland: native perennial and non‐native annual grasses. We first characterized pathogen community composition and disease severity of the two host groups to approximate differences in competence. We then used observational and manipulated gradients of native perennial and non‐native annual grass densities to assess the effects of each host group on pathogen community composition and disease severity in 1‐m2 plots.Native perennial and non‐native annual grasses hosted distinct pathogen communities but shared generalist pathogens. Native perennial grasses experienced 26% higher disease severity than non‐native annuals. Only the observational gradient of native perennial grass density affected disease severity; there were no other significant relationships between host group density and either disease severity or pathogen community composition.Synthesis. The life and evolutionary histories of grasses likely influence their competence for different pathogen species, exemplified by distinct pathogen communities and differences in disease severity. However, there was limited evidence that the density of either host group affected pathogen community composition or disease severity. Therefore, competence for different pathogens likely shapes pathogen community composition and disease severity but may not interact with host density to alter disease risk and impacts at small scales. [ABSTRACT FROM AUTHOR]

Landscape permeability is often explored spatially, but may also vary temporally. Landscape permeability, including partial barriers, influences migratory animals that move across the landscape. Partial barriers are common in rivers where barrier passage varies with streamflow. We explore the influence of partial barriers on the spatial and temporal distribution of migration‐linked genotypes of Oncorhynchus mykiss, a salmonid fish with co‐occurring resident and migratory forms, in tributaries to the South Fork Eel River, California, USA, Elder and Fox Creeks. We genotyped >4,000 individuals using RAD‐capture and classified individuals as resident, heterozygous or migratory genotypes using life history‐associated loci. Across four years of study (2014–2017), the permeability of partial barriers varied across dry and wet years. In Elder Creek, the largest waterfall was passable for adults migrating up‐river 4–39 days each year. In this stream, the overall spatial pattern, with fewer migratory genotypes above the waterfall, remained true across dry and wet years (67%–76% of migratory alleles were downstream of the waterfall). We also observed a strong relationship between distance upstream and proportion of migratory alleles. In Fox Creek, the primary barrier is at the mouth, and we found that the migratory allele frequency varied with the annual timing of high flow events. In years when rain events occurred during the peak breeding season, migratory allele frequency was high (60%–68%), but otherwise it was low (30% in two years). We highlight that partial barriers and landscape permeability can be temporally dynamic, and this effect can be observed through changing genotype frequencies in migratory animals. [ABSTRACT FROM AUTHOR]

Avian incubation provides an opportunity to test how parental behavior and ecological conditions interact to shape variation in offspring traits along geographic gradients. In particular, the duration of the incubation period is shorter at higher latitudes, but the degree to which this pattern arises from genetic divergence in rates of growth and development versus from parentally‐mediated variation in egg temperatures is controversial. At higher latitudes parents have higher daytime incubation attentiveness, i.e. they spend a greater proportion of the day on the nest. However, interpreting latitudinal variation in behavior is complicated by latitudinal patterns in ambient temperature and day length. Here, we use 24‐h video recordings to compare the incubation behavior of orange‐crowned warblers Leiothlypis celata in California and Alaska and test how attentiveness varies between populations and as a function of temperature. Birds in Alaska had higher nest attentiveness during the day, despite experiencing similar ambient temperatures. However, when analyzed over 24‐h, the longer nighttime period in California almost entirely canceled out daytime attentiveness differences between populations, and differences in 24‐h attentiveness were small. Our work highlights how incorporating nighttime incubation behavior qualitatively alters latitudinal patterns of attentiveness, and how lower ambient temperatures cannot account for the higher attentiveness in a high latitude population. These populations differ in their incubation period lengths, and differentiating between evolved versus environmentally‐induced variation in offspring growth and development will help understand the fitness consequences of variation in developmental periods. [ABSTRACT FROM AUTHOR]

Many migratory species, from monarch butterflies to wildebeest, express partial migration, where only a subset of a population migrates. This intraspecific variation is likely to have large ecological consequences. We studied the ecological consequences of partial migration in a salmonid fish, Oncorhynchus mykiss, in coastal streams in California, USA. One ecotype, steelhead trout, migrates to the ocean, whereas the other, rainbow trout, completes its lifecycle in freshwater. Migration has a strong genetic basis in O. mykiss. In one stream, we found differences in the frequency of migration-linked genotypes below and above a waterfall barrier (migratory allele frequency of 60% below vs. 31% above). Below the waterfall, in the migratory-dominated region, the density of young fish (<1 yr old) was approximately twice that in the resident-dominated region above the waterfall (0.46 vs. 0.26 individuals/m2, respectively), presumably reflecting the higher fecundity of migratory females. Additionally, there were half as many older fish (>1 yr old) in pools downstream of the waterfall (0.05 vs. 0.13 individuals/m2). In a second stream, between-year variation in the dominance of migratory vs. resident fish allowed us to explore differences in fish density and size structure through time, and we found a consistent pattern. In brief, when migratory genotypes dominated, we found higher densities of young fish and lower densities of older fish, resulting in a simpler size structure, compared to when resident genotypes dominated. Moreover, large resident trout had a slightly higher trophic position than young fish (3.92 vs. 3.42 in one creek and 3.77 vs. 3.17 in the other), quantified with stable isotope data. The difference in fish size structure did not generate trophic cascades. Partial migration is widespread among migratory populations, as is phenotypic divergence between resident and migratory forms, suggesting the potential for widespread ecological effects arising from this common form of intraspecific variation. [ABSTRACT FROM AUTHOR]

One of the strongest biological impacts of climate change has been the movement of species poleward and upward in elevation. Yet, what is not clear is the extent to which the spatial distribution of locally adapted lineages and ecologically important traits may also shift with continued climate change. Here, we take advantage of a transplant experiment mimicking up‐slope seed dispersal for a suite of ecologically diverse populations of yellow monkeyflower (Mimulus guttatus sensu lato) into a high‐elevation common garden during an extreme drought period in the Sierra Nevada mountains, California, USA. We use a demographic approach to quantify fitness and test for selection on life history traits in local versus lower‐elevation populations and in normal versus drought years to test the potential for up‐slope migration and phenotypic selection to alter the distribution of key life history traits in montane environments. We find that lower‐elevation populations tend to outperform local populations, confirming the potential for up‐slope migration. Although selection generally favored some local montane traits, including larger flowers and larger stem size at flowering, drought conditions tended to select for earlier flowering typical of lower‐elevation genotypes. Taken together, this suggests that monkeyflower lineages moving upward in elevation could experience selection for novel trait combinations, particularly under warmer and drier conditions that are predicted to occur with continued climate change. [ABSTRACT FROM AUTHOR]

The timing of life history events, such as germination and reproduction, influences ecological and selective environments throughout the life cycle. Many organisms evolve responses to seasonal environmental cues to synchronize these key events with favourable conditions. Often the fitness consequences of each life history transition depend on previous and subsequent events in the life cycle. If so, shifts in environmental cues can create cascading effects throughout the life cycle, which can influence fitness, selection on life history traits, and population viability.We examined variation in cue responses for contingent life history expression and fitness in a California native wildflower, Streptanthus tortuosus, by manipulating seasonal germination timing in a common garden experiment. We also manipulated chilling exposure to test the role of vernalization cues for seasonal life history contingency.Plants germinating early in the growing season in autumn were more likely to flower in the first year and less likely to perennate than later germinants in spring. First‐year reproduction and overall fitness was the highest for autumn cohorts. Sensitivity analyses showed that optimal germination date depended on survival beyond the first year and fruit production in later years.Experimental chilling exposure induced first‐year flowering in spring germinants, demonstrating that seasonal life history contingency is mediated by a vernalization requirement. This requirement reduced fitness of spring germinants without increasing survival or later fecundity and may be maladaptive. Such mismatches between cues and fitness may become more pervasive as predicted climate change reduces exposure to chilling, shortens growing seasons, and increases severity of summer drought.Synthesis. Shifts in germination timing in seasonal environments can cause cascading effects on trait expression and fitness that extend beyond the first year of the life cycle. Climate change is likely to shift seasonal conditions, influencing such life history contingency, with significant impacts on trait expression, fitness, and population persistence. These shifts may cause strong natural selection on cue sensitivity and life history expression, but it is an open question whether populations have the potential for rapid adaptation in response to this selection. [ABSTRACT FROM AUTHOR]

In this paper, I describe for the first time the migratory life cycle of an univoltine mayfly, Ephemerella maculata (Traver, 1934), between mainstems and tributaries of stream networks in California. Ephemerella maculata nymphs grow in sunny open mainstems and then emerge. Female adults fly into adjacent shaded tributaries, oviposit eggs, and die. The eggs diapause over summer and hatch in the fall in tributaries; then small nymphs drift down back to the mainstem before the subsequent spring growing season. Isotope analyses validate the adult migrations from mainstem to tributaries. Field rearing experiments show that the abundant algae in sunny mainstems are important food for the growth of E. maculata nymphs. However, eggs survive and hatch equally well in mainstem and tributaries, therefore, the fitness advantage of their migration to tributaries remains unclear. [ABSTRACT FROM AUTHOR]

The Calico Surfperch (Amphistichus koelzi) shares a similar size, morphology and feeding habitat with its 2 widely-sympatric congeners, the Barred Surfperch (Amphistichus argenteus) and Redtail Surfperch (Amphistichus rhodoterus). Like the other 2 species, A. koelzi is an important commercial and recreational resource, but unlike these species, A. koelzi has received virtually no attention in the scientific literature. We found average relative fecundity to be significantly higher than in A. koelzi's 2 congeners, A. argenteus and A. rhodoterus, and the slope of the regression of brood count on female size in A. koelzi was steeper and translated to the left of the same slopes representing the 2 congeners. [ABSTRACT FROM AUTHOR]

Land-use change frequently reduces local species diversity. Species losses will often result in loss of trait diversity, with likely consequences for community functioning. However, the converse need not be generally true: management approaches that succeed in retaining species richness could nevertheless fail to maintain trait diversity. We evaluated this possibility using bee communities in a California agroecosystem., We examined among site patterns in bee species diversity and functional-trait diversity in a landscape composed of a mosaic of semi-natural habitat, organic farms and conventional farms. We sampled bees from all three habitat types and compiled a data base of life-history ('functional') traits for each species., Although species richness was higher on organic farms than conventional farms, functional diversity was lower in both farm types than in natural habitat. Nesting location (below-ground vs. above-ground) was the primary trait contributing to differences in functional diversity between farms and natural habitat, reflecting observed differences in availability of nesting substrates among habitat types. Other traits, including phenology and sociality, were also associated with species' occurrences or dominance in particular site types. These patterns suggest that management practices common to all farms act as environmental filters that cause similarly low functional diversity in their bee communities., Synthesis and applications. Although our results support the value of organic farming in maintaining abundant and species-rich bee communities, components of bee functional diversity are not well supported in farmed landscapes, regardless of farming practice. Maintenance of natural habitat, and/or the addition of natural habitat elements to farms, is therefore important for the retention of functionally diverse bee assemblages in agroecosystems. [ABSTRACT FROM AUTHOR]

We used acoustic telemetry to study the post-spawn movement of Oncorhynchus mykiss kelts released in April 2005 and 2006 from the Coleman National Fish Hatchery, Anderson, CA. Following release, O. mykiss kelts demonstrated both anadromous and non-anadromous life histories, with some fish alternating life history strategies between years. Anadromy was most common, characterized by a short-term residence near the release site, followed by sustained downstream emigration once initiated. O. mykiss kelts demonstrating anadromy arrived at the Golden Gate Bridge from April to mid-July. Repeat spawning migrations of anadromous O. mykiss kelts began from late-September through October of the year of release. High fidelity back to Battle Creek was observed, occurring from late-September through November. While most O. mykiss kelts were anadromous, at least 10 % remained in freshwater, or residualized. O. mykiss kelts that residualized demonstrated two distinct patterns of movement: 1) residency near the release location, and 2) potamodromy. Overall survival was high with 36 % and 48 % of O. mykiss kelts released making a repeat spawning migration and demonstrating iteroparity in 2005 and 2006, respectively. Increase in body lengths of O. mykiss kelts that returned to the Coleman NFH were significantly greater for anadromous fish, compared to fish that residualized, but survival was higher for fish that residualized. Release of hatchery O. mykiss kelts could result in both positive and negative genetic and ecological effects to hatchery- and naturally-producing salmonids. We believe the benefits of releasing O. mykiss kelts at the Coleman NFH, including increased numbers and size of fish in the recreational fishery and genetic and demographic benefits to the hatchery brood stock outweigh the limited risk to natural populations that would result from predation and competition of the relatively small number of O. mykiss kelts that resided in fresh water. [ABSTRACT FROM AUTHOR]

Comparative evaluations of population dynamics in species with temporal and spatial variation in life-history traits are rare because they require long-term demographic time series from multiple populations. We present such an analysis using demographic data collected during the interval 1978-1996 for six populations of western terrestrial garter snakes (Thamnophis elegans) from two evolutionarily divergent ecotypes. Three replicate populations from a slow-living ecotype, found in mountain meadows of northeastern California, were characterized by individuals that develop slowly, mature late, reproduce infrequently with small reproductive effort, and live longer than individuals of three populations of a fast-living ecotype found at lakeshore locales. We constructed matrix population models for each of the populations based on 8-13 years of data per population and analyzed both deterministic dynamics based on mean annual vital rates and stochastic dynamics incorporating annual variation in vital rates. (1) Contributions of highly variable vital rates to fitness (?s) were buffered against the negative effects of stochastic variation, and this relationship was consistent with differences between the meadow (M-slow) and lakeshore (L-fast) ecotypes. (2) Annual variation in the proportion of gravid females had the greatest negative effect among all vital rates on ?s. The magnitude of variation in the proportion of gravid females and its effect on ?s was greater in M-slow than L-fast populations. (3) Variation in the proportion of gravid females, in turn, depended on annual variation in prey availability, and its effect on ?s was 4-23 times greater in M-slow than L-fast populations. In addition to differences in stochastic dynamics between ecotypes, we also found higher mean mortality rates across all age classes in the L-fast populations. Our results suggest that both deterministic and stochastic selective forces have affected the evolution of divergent life-history traits in the two ecotypes, which, in turn, affect population dynamics. M-slow populations have evolved life-history traits that buffer fitness against direct effects of variation in reproduction and that spread lifetime reproduction across a greater number of reproductive bouts. These results highlight the importance of long-term demographic and environmental monitoring and of incorporating temporal dynamics into empirical studies of life-history evolution. [ABSTRACT FROM AUTHOR]

Abstract: Some populations of gelatinous zooplankton appear to be increasing and causing ecological disruptions during large bloom events. The goal of this study was to investigate the life history and population dynamics of the small, invasive Moerisia sp. and its potential ecological impacts in the upper San Francisco Estuary, California. Medusae and polyps were collected from 8 and 2 sites, respectively, during 2007 and 2008. Polyps emerged from a resting stage during June. Asexual reproduction of medusae buds was positively correlated with temperature and negatively related to salinity. The production of polyp buds was positively correlated with dissolved oxygen and water transparency levels. Sexual reproduction, defined by the presence of eggs, was related to the size of medusae. Cessation of reproduction of both polyps and medusae occurred in October, when temperatures dropped below 17 °C. This life history is similar to other hydrozoans and allows Moerisia sp. to reach large numbers seasonally in the San Francisco Estuary, possibly contributing to the recent declines of pelagic fish and zooplankton. [Copyright &y& Elsevier]

Abstract: The butterfly fauna at Willow Slough, Yolo County, California has been censused for 32years as part of a participatory citizen-science project, the Fourth of July Butterfly Count. While the utility of a once-a-year census as a monitoring tool is potentially compromised by lack of standardization in counting protocols and variation in observer skill, at Willow Slough these issues have been minimized. We examined the Willow Slough count data for trends in both faunal diversity and the probability of presence of individual species. During the study, the number of species observed at a visit declined by 39%. Regressions of per-visit species counts against time did not detect a statistically significant decline until year 24. In contrast, Fisher’s α, a statistic designed to reduce sample-size bias, detected the decline as early as year 13. Twelve of the 24 species analyzed showed significant declines in probability of occurrence; a further nine exhibited negative but non-significant trends. Butterflies that overwinter as eggs or larvae were more likely to decline than those that overwinter as pupae or adults. Many species in decline at Willow Slough have also been observed less frequently at nearby sites which are monitored year-round, supporting the value of once-a-year monitoring. Although correlations with climatic data have been identified, they are too weak to account for the observed faunal decline. We suspect broader patterns of land use and habitat continuity are implicated in butterfly declines across the region. We conclude that once-a-year sampling, if properly and rigorously done, is in fact useful as a monitoring tool for butterfly faunas, and that Fisher’s α is well suited to early detection of trends in repeated diversity sampling. [Copyright &y& Elsevier]

The article discusses a study on the possibility that a trade-off between reproductive and immune processes occurs in a wild population of female sagebrush lizards known as Sceloporus graciosus during the breeding season in the San Jacinto mountains of southern California. The study tested the hypothesis that such a trade-off could be eliminated in females by means of food supplementation. The orange side coloration of female lizards was measured to determine their reproductive state. Innate immunity was determined by calculating the capability of collected plasma to kill Escherichia coli bacteria. According to the authors, the energetic state of the lizards is the primary factor that influence such trade-offs.

Abstract: Comparative hormone studies can reveal how physiology underlies life history variation. Here, we examined seasonal variation in plasma testosterone concentration between populations of male orange-crowned warblers (Vermivora celata) breeding in Fairbanks, Alaska (V. c. celata) and on Santa Catalina Island, California (V. c. sordida). These populations face different ecological constraints and exhibit different life histories. Alaska birds have a short breeding season, low annual adult survival, and high reproductive rates. In contrast, Catalina Island birds exhibit high adult survival and low reproductive rates despite having a long breeding season. We examined seasonal variation in male testosterone concentrations as a potential mechanism underlying differences in male reproductive strategies between populations. From 2006 to 2008, we sampled males during the pre-incubation, incubation, and nestling stages. Alaska males exhibited a seasonal testosterone pattern typical of northern passerines: testosterone levels were high during pre-incubation and declined during incubation to low levels during nestling provisioning. Testosterone concentrations in Catalina Island males, however, did not vary consistently with breeding stage, remained elevated throughout the breeding season, and were higher than in Alaska males during the nestling stage. We hypothesize that in Alaska, where short seasons and high adult mortality limit breeding opportunities, the seasonal testosterone pattern facilitates high mating effort prior to incubation, but high parental investment during the nestling stage. On Catalina Island, elevated testosterone levels may reflect the extended mating opportunities and high population density facing males in this population. Our results suggest that population variation in seasonal testosterone patterns in orange-crowned warblers may be a function of differences in life history strategy and the social environment. [ABSTRACT FROM AUTHOR]

Adaptation to novel habitats and phenotypic plasticity can be counteracting forces in evolution, but both are key characteristics of the life history of steelhead/rainbow trout (Oncorbynchus mykiss). Anadromous steelhead reproduce in freshwater river systems and small coastal streams but grow and mature in the ocean. Resident rainbow trout, either sympatric with steelhead or isolated above barrier dams or waterfalls, represent an alternative life-history form that lives entirely in freshwater. We analyzed population genetic data from 1486 anadromous and resident 0. mykiss from a small stream in coastal California with multiple barrier waterfalls. Based on data from 18 highly variable microsatellite loci (He = 0.68), we conclude that the resident population above one barrier, Big Creek Falls, is the result of a recent anthropogenic introduction from the anadromous population of 0. mykiss below the falls. Furthermore, fish from this above-barrier population occasionally descend over the falls and have established a genetically differentiated below-barrier subpopulation at the base of the falls, which appears to remain reproductively isolated from their now-sympatric anadromous ancestors. These results support a hypothesis of rapid evolution of a purely resident life history in the above-barrier population in response to strong selection against downstream movement. [ABSTRACT FROM AUTHOR]

All bears give birth to highly altricial young, but maternal style is markedly divergent among species. Like many aspects of sun bear (Helarctos maluyanus) life history, maternal care in this species is poorly documented. Using detailed systematic behavioral observations, we provide the first quantitative report on the mother-cub relationship and early behavioral development in a sun bear. We summarize temporal changes in mother-cub behavior as the cub ages and evaluate maternal investment in the cub. We also provide developmental milestones documented in 2 cubs born (one in 2004, one in 2006) at the San Diego Zoo and compare them with those available in the literature. This sun bear mother displayed behavior indicating a high level of behavioral investment in young offspring while still in the den. She held the cub off the ground, cradled it to reduce the cub's exposure to ambient air, and was attentive to the cub's needs, responding to nearly 50% of the cub's vocalizations and grooming the cub frequently. We conclude that the maternal care behavior of sun bears appears to be active, comparable to the giant panda (Ailuropoda melanoleuca) and different from the more passive maternal care displayed by American black (Ursus americanus) and brown bears (U. arctos) during the denning phase. A growing number of studies of maternal care in ursids are beginning to provide insights into comparative life histories. [ABSTRACT FROM AUTHOR]

Abstract: The desert tortoise occurs in two strikingly different desert regimes in the southwestern United States. In the Mojave Desert, rainfall is more irregular and resources are more limited than in the Sonoran Desert. We examined the age structure of tortoise populations from these two deserts to determine whether the difference in resource availability has driven an evolutionary divergence in life history strategies. Age and growth rates strongly reflect the ecological adaptation of the two populations. The oldest Sonoran males reached 54years, compared to only 43years in females. The oldest West Mojave (WM) males reached 56years, compared to only 27years in females. WM tortoises grew faster than Sonoran ones, and females reached sexual maturity at earlier ages (∼17–19years) than Sonoran females (∼22–26years). These traits and the higher rate of clutch production in the WM population are likely the evolutionary adaptation for low juvenile survivorship and a significantly shorter life span. Frequent droughts in the WM Desert and the lowest annual rainfall area within the range of the desert tortoise cause chronic physiological stress, likely annually, and are proposed as a major selection force producing contrasting life-history strategies. [Copyright &y& Elsevier]

Clines of biological variation result from variation in physical environmental conditions. We report new reproductive data for a population of antelope ground squirrels, Ammospermophilus leucurus, at the northern geographic limit of this species. We then analyze reproductive patterns at 3 sites spanning the entire north-south extent of the geographic range, covering more than 2,500 km and 21 degrees of latitude. The overall breeding season of populations is relatively short in Oregon (42°N) and California (37°N), but in Baja California (24°N) it encompasses half a year. Mean litter size decreases significantly from north to south, from 9.3 (SD = 1.8) per litter in Oregon to 5.9 (SD = 1.5) in Baja California. Major shifts in seasonality of precipitation and ecosystem composition and diversity are associated with longer breeding season and lower litter size at the southern geographic extreme of A. leucurus. The environmental predictability for the northern populations is due to "constancy," whereas the predictability at the southern extreme is due to "contingency." The observed latitudinal reproductive patterns represent local responses of populations to environmental conditions and the related characteristics of North America's major desert ecosystems. [ABSTRACT FROM AUTHOR]

Life-history theory predicts that longer-lived, less fecund species should take fewer risks when exposed to predation than shorter-lived, more fecund species. We tested this prediction for seven species of dabbling ducks (Anas) by measuring the approach behavior (behavior of ducks when approaching potential landing sites) of 1099 duck flocks during 37 hunting trials and 491 flocks during 13 trials conducted immediately after the 1999-2000 waterfowl hunting season in California, USA. We also experimentally manipulated the attractiveness of the study site by using two decoy treatments: (1) traditional, stationary decoys only, and (2) traditional decoys in conjunction with a mechanical spinning-wing decoy. Approach behavior of ducks was strongly correlated with their life history. Minimum approach distance was negatively correlated with reproductive output during each decoy treatment and trial type. Similarly, the proportion of flocks taking risk (approaching landing sites to within 45 m) was positively correlated with reproductive output. We found similar patterns of approach behavior in relation to other life-history parameters (i.e., adult female body mass and annual adult female survival rate). Thus, species characterized by a slower life-history strategy (e.g., Northern Pintail [A. acuta]) were more risk-averse than species with a faster life-history strategy (e.g., Cinnamon Teal [A. cyanoptera]). Furthermore, although we were able to reduce risk-averseness using the spinning-wing decoy, we were unable to override the influence of life history on risk-taking behavior. Alternative explanations did not account for the observed correlation between approach behavior and life-history parameters. These results suggest that life history influences the risk-taking behavior of dabbling ducks and provide an explanation for the differential vulnerability of waterfowl to harvest. [ABSTRACT FROM AUTHOR]

Mastocarpus papillatus is one of the most common intertidal red algae on the central California coast. Mastocarpus papillatus follows the typical red algal sexual life cycle. Studies indicate that individual female gametophytes are obligated to their particular mode of reproduction as all spores cultured from a single blade produce the same life history stage. Genetic diversity has been evaluated as high as the genus level on the genetic basis of amplified fragment length polymorphism (AFLP) fingerprints. AFLPs provide quick, inexpensive, reliable DNA fingerprints without extensive foreknowledge of the study organism's genome.

Abstract Annual grasslands in California are often managed with seasonal grazing and prescribed burning on the assumption that such practices have long-term benefits for native species. Mature native perennial bunchgrasses, particularly Nassella pulchra (purple needlegrass), are often the focal species, although very little is known about responses at different life history stages. Thus, important questions remain about long-term population dynamics of both mature plants and seedling recruitment. In plots receiving repeated grazing and burning events over 7 years, mortality of mature plants was threefold higher on mounds than on intermounds and likely reflected increased competition intensity associated with increased resource availability in deeper soil. Burning and grazing treatments had strong positive effects on basal area of mature N. pulchra . However, plants in grazed plots that were not burned contained considerable standing dead biomass. Topographic location strongly influenced growth as intermound plants grew relatively more than mound plants, but the effects on growth of burning and grazing did not vary with topographic location. In mapped plots N. pulchra recruitment was very low, and overall density dropped an average of 31%. However, a significant time-by-burning effect indicated that survival was significantly higher in burned plots. After 7 years of repeated treatments, effects of burning and grazing management on mature N. pulchra were positive but not for all phenological stages. Understanding long-term influence of management on bunchgrass populations may not be easy to determine because short-term results may not reflect long-term responses and some life cycle dynamics may be observed only over very long periods. [ABSTRACT FROM AUTHOR]

Longitudinal reproductive and mortality data collected from two colonies of Hanuman langur monkeys (Presbytis entellus) in California (University of California, Berkeley; San Diego Zoo) are presented. Approximately 10 years of data from each facility reveal that langur monkey females reach reproductive maturity between 3 and 5 years and have median birth intervals, following the birth of a live infant that survives beyond 9 months, of approximately 15.5 months. Births are not seasonal at either facility and pregnancy failure rates at UCB are approximately 30%. Mortality of subadults was highest during the neonatal period (<30 days), and probability of survivorship at 5 years is between .41 and .50. Observed differences and similarities in patterns of reproduction and mortality between the two colonies and field populations are discussed. [ABSTRACT FROM AUTHOR]

Thermal stress experiments are essential for understanding organisms' thermal limits and the physiological processes that contribute to establishing those limits. Experiments typically employ either an abrupt transfer to near-lethal temperatures or a gradually increasing thermal exposure. In the current study, we used three populations of the intertidal copepod Tigriopus californicus that are known to differ in upper thermal tolerance to investigate the effects of gradual versus abrupt thermal exposures on survivorship, developmental time, and heat shock protein gene expression. The developmental rate of nauplii was unaffected following the gradual exposure, whereas developmental time slowed by ∼2 d (∼20%) following an abrupt exposure. The gradual exposure also improved survivorship in comparison to the abrupt exposure. Furthermore, the heat shock protein genes hsp70 and hspb1 showed greater upregulation during the gradual thermal exposure compared to the abrupt exposure. Though the differences in response to each thermal regime varied in magnitude among the different populations, the types of responses were very similar (i.e., following the gradual exposure survivorship increased, developmental time showed no effect, and heat shock protein gene upregulation during the exposure increased). Therefore, the enhanced protective effect of the heat shock response during gradual exposures appears to be conserved within the species despite population-level differences in thermal tolerance. Thus, an ecologically relevant thermal exposure likely enables improved cellular protective mechanisms by allowing for an effective and timely heat shock response, which plays a role in mitigating the effects of thermal stress and thereby enhances tolerance to elevated temperatures.

Juvenile steelhead Oncorhynchus mykiss from a northern California Central Valley population were reared in a controlled laboratory experiment. Significantly different rates of growth were observed among fish reared under two ration treatments and three temperature treatments (8, 14 and 20°C). Wider circulus spacing and faster deposition was associated with faster growth. For the same growth rate, however, circulus spacing was two-fold wider and deposited 36% less frequently in the cold compared to the hot temperature treatment. In a multiple linear regression, median circulus spacing and water temperature accounted for 68% of the variation in observed O. mykiss growth. These results corroborate previous research on scale characteristics and growth, while providing novel evidence that highlights the importance of water temperature in these relationships. Thus, this study establishes the utility of using scale analysis as a relatively non-invasive method for inferring growth in salmonids., (© 2013 The Fisheries Society of the British Isles.)

Observations on distribution, water quality, habitat and avoidance behavior are presented. for Eubranchipus bundyi, Eubranchipus oregonus, and Eubranchipus serratus (Chirocephalidae) in California, USA. Allthree species were previously known within California from single localities. Two new localities for E. oregonus in Tuolumne County and in Humbolt County and 21 new localities for E. serratus in Lassen and Shasta Counties are presented. The E. oregonus localities represent substantial range extensions within California, while the E. serratus localities show a large number of populations within the surveyed area. In occupied pools, pH ranged from 5.5 to 9.0, conductivity from 30to 150 mu S, turbidity (NTU) from 0.8 to 140.0 and total alkalinity from 68 to 128 mg l-1. Pool size varied from small seasonal pools of a few meters in diameter to large seasonal lakes several kilometers across. Limited survey effort and successful 'predator' avoidance by the shrimp may have contributed to the lack of distributional information for these species in California. [ABSTRACT FROM AUTHOR]