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Extensive sampling around Martinique during the Muséum National d’Histoire Naturelle ‘Madibenthos’ expedition in 2016 resulted in a collection of hundreds of alpheid shrimps, of which 21 distinct species of Synalpheus Spence Bate, 1888 are studied herein. Combining results of a morphological analysis, a phylogenetic tree (combined 16S and COI) and species delimitation analyses (ABGD and PTP) indicates three species as new to science. These species are S. chaki sp. nov., S. corbariae sp. nov., and S. macdonaldi sp. nov. The first two new species belong to the S. rathbunae Coutière, 1909 species group, whereas the third new species broadly groups with the S. gambarelloides group. Additionally, 13 new country records of Synalpheus are reported for Martinique.

Across plants and animals, genome size is often correlated with life-history traits: large genomes are correlated with larger seeds, slower development, larger body size and slower cell division. Among decapod crustaceans, caridean shrimps are among the most variable both in terms of genome size variation and life-history characteristics such as larval development mode and egg size, but the extent to which these traits are associated in a phylogenetic context is largely unknown. In this study, we examine correlations among egg size, larval development and genome size in two different genera of snapping shrimp, Alpheus and Synalpheus, using phylogenetically informed analyses. In both Alpheus and Synalpheus, egg size is strongly linked to larval development mode: species with abbreviated development had significantly larger eggs than species with extended larval development. We produced the first comprehensive dataset of genome size in Alpheus (n = 37 species) and demonstrated that genome size was strongly and positively correlated with egg size in both Alpheus and Synalpheus. Correlated trait evolution analyses showed that in Alpheus, changes in genome size were clearly dependent on egg size. In Synalpheus, evolutionary path analyses suggest that changes in development mode (from extended to abbreviated) drove increases in egg volume; larger eggs, in turn, resulted in larger genomes. These data suggest that variation in reproductive traits may underpin the high degree of variation in genome size seen in a wide variety of caridean shrimp groups more generally.

Extensive sampling around Martinique during the Muséum National d’Histoire Naturelle ‘Madibenthos’ expedition in 2016 resulted in a collection of hundreds of alpheid shrimps, of which 21 distinct species of Synalpheus Spence Bate, 1888 are studied herein. Combining results of a morphological analysis, a phylogenetic tree (combined 16S and COI) and species delimitation analyses (ABGD and PTP) indicates three species as new to science. These species are S. chaki sp. nov., S. corbariae sp. nov., and S. macdonaldi sp. nov. The first two new species belong to the S. rathbunae Coutière, 1909 species group, whereas the third new species broadly groups with the S. gambarelloides group. Additionally, 13 new country records of Synalpheus are reported for Martinique.

Este artículo contiene 7 páginas, 3 figuras, 1 tabla., The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of consumption peaked at midlatitudes (25 to 35°) in both Northern and Southern Hemispheres across both seagrass and unvegetated sediment habitats. This pattern contrasts with terrestrial systems, where biotic interactions reportedly weaken away from the equator, but it parallels an emerging pattern of a subtropical peak in marine biodiversity. The higher consumption at midlatitudes was closely related to the type of consumers present, which explained rates of consumption better than consumer density, biomass, species diversity, or habitat. Indeed, the apparent effect of temperature on consumption was mostly driven by temperature-associated turnover in consumer community composition. Our findings reinforce the key influence of climate warming on altered species composition and highlight its implications for the functioning of Earth’s ecosystems., We acknowledge funding from the Smithsonian Institution and the Tula Foundation.

Eusocial animals often achieve ecological dominance in the ecosystems where they occur, a process that may be linked to their demography. That is, reproductive division of labor and high reproductive skew in eusocial species is predicted to result in more stable effective population sizes that may make groups more competitive, but also lower effective population sizes that may make groups more susceptible to inbreeding and extinction. We examined the relationship between demography and social organization in one of the few animal lineages where eusociality has evolved recently and repeatedly among close relatives, theSynalpheussnapping shrimps. Although eusocial species often dominate the reefs where they occur by outcompeting their non-eusocial relatives for access to sponge hosts, many eusocial species have recently become extirpated across the Caribbean. Coalescent-based historical demographic inference in 12 species found that across nearly 100,000 generations, eusocial species tended to have lower but more stable effective population sizes through time. Our results are consistent with the idea that stable population sizes may enable eusocial shrimps to be more competitively dominant, but they also suggest that recent population declines are likely caused by eusocial shrimps’ heightened sensitivity to anthropogenically-driven environmental changes as a result of their low effective population sizes and localized dispersal, rather than to natural cycles of inbreeding and extinction. Thus, although the unique life histories and demography of eusocial shrimps has likely contributed to their persistence and ecological dominance over evolutionary timescales, these social traits may also make them vulnerable to contemporary environmental change.

Although crustaceans vary extensively in genome size, little is known about how genome size may affect the ecology and evolution of species in this diverse group, in part due to the lack of large genome size datasets. Here we investigate interspecific, intraspecific, and intracolony variation in genome size in 39 species of Synalpheus shrimps, representing one of the largest genome size datasets for a single genus within crustaceans. We find that genome size ranges approximately 4-fold across Synalpheus with little phylogenetic signal, and is not related to body size. In a subset of these species, genome size is related to chromosome size, but not to chromosome number, suggesting that despite large genomes, these species are not polyploid. Interestingly, there appears to be 35% intraspecific genome size variation in Synalpheus idios among geographic regions, and up to 30% variation in Synalpheus duffyi genome size within the same colony.

Although background matching is a common form of camouflage across a wide diversity of animals, there has been surprisingly little experimental work testing the fitness consequences of this camouflage strategy, especially in marine ecosystems. In this study, we tested whether color camouflage enhances survival of the intertidal marine isopod Pentidotea (Idotea) wosnesenskii, quantified patterns of camouflage in different algal habitats, and examined how algal diet affected color change and growth using laboratory assays. In the field, isopods collected from two differently colored algal habitats (the brown alga Fucus distichus and the red alga Odonthalia floccosa) matched the color of their respective algal habitats, and also differed significantly in body size: smaller red isopods were found on red algae, while larger brown isopods were found on brown algae. Predation experiments demonstrated these color differences had fitness benefits: brown isopods that matched their brown algae habitats survived at higher rates than red unmatched isopods. Surprisingly, despite the propensity of isopods to match their algal habitats, algal diet had no effect on color change in color change experiments. Instead, isopods in all treatments turned browner, matching the color of the algal habitat that many isopods are found on as adults. In summary, our data supported our hypothesis that background matching serves an adaptive function in reducing predation, with important evolutionary implications for explaining the wide variation in color change mechanisms in idoteid isopods.

The species-complex of Synalpheus paraneptunusCoutiere, 1909 is one of the most behaviorally and sexually diverse groups of sponge-dwelling shrimp in Synalpheus, containing both eusocial and pair-living species. Accurate resolution of this taxonomically challenging group is crucial to examining the evolution of social behavior in the genus. New collections from the US Florida Keys and Cuba, along with examination of previous collections from Jamaica, Panama and Belize, have yielded two new species: the eusocial Synalpheus cayoneptunusn. sp. (described from type material from the Florida Keys), and Synalpheus ankerin. sp. (described from type material from Belize). Synalpheus duffyiAnker and Toth, 2008 is reported from new locations in Cuba and the Florida Keys. A phylogenetic analysis of six of the nine species in the S. paraneptunus-species-complex indicates that eusociality likely arose only once in this complex but was secondarily lost in the pair-living species S. ankeri. A key to the nine known species in the complex is presented based on morphological characters.

A new, conspicuously coloured species of the alpheid genus Synalpheus Spence Bate, 1888, is described based on material collected on the Pacific coast of Panama. Synalpheus pinkfloydi sp. nov. is closely related to the western Atlantic S. antillensis Coutière, 1909, the two taxa being transisthmian, cryptic sister species. Both species are characterised by the distal areas of their major and minor chelae coloured in an intense, almost glowing pink-red. The morphological differences between S. pinkfloydi sp. nov. and S. antillensis Coutière, 1909 are subtle, being limited to the slightly different proportions of the merus of both chelipeds, distodorsal armature of the major cheliped merus, relative length of the antennal scaphocerite, and body size. However, they are genetically different with a 10.2% sequence divergence in COI. Based on molecular clock estimates, these transisthmian taxa diverged around 6.8–7.8 mya, i.e. well before the final closure of the Isthmus of Panama 2.5–3 mya.

Evidence from insects and vertebrates suggests that cooperation may have enabled species to expand their niches, becoming ecological generalists and dominating the ecosystems in which they occur. Consistent with this idea, eusocial species of sponge-dwelling Synalpheus shrimps from Belize are ecological generalists with a broader host breadth and higher abundance than non-eusocial species. We evaluate whether sociality promotes ecological generalism (social conquest hypothesis) or whether ecological generalism facilitates the transition to sociality (social transition hypothesis) in 38 Synalpheus shrimp species. We find that sociality evolves primarily from host generalists, and almost exclusively so for transitions to eusociality. Additionally, sponge volume is more important for explaining social transitions towards communal breeding than to eusociality, suggesting that different ecological factors may influence the independent evolutionary origins of sociality in Synalpheus shrimps. Ultimately, our results are consistent with the social transition hypothesis and the idea that ecological generalism facilitates the transition to sociality.

The snapping shrimp genus Synalpheus (Alpheidae) is one of the most speciose decapod genera, with over 160 described species worldwide. Most species live in symbiotic relationships with other marine organisms, such as sponges, corals and crinoids, and some sponge-dwelling species have a highly organized, social structure. The present study is the first worldwide molecular phylogenetic analysis of Synalpheus, based on >2,200 bp of sequence data from two mitochondrial (COI and 16S) and two nuclear (PEPCK and 18S) loci. Our molecular data show strong support for monophyly of three out of six traditionally recognized morphology-based species groups: the S. brevicarpus, S. comatularum and S. gambarelloides groups. The remaining three species groups (S. paulsoni, S. neomeris and S. coutierei groups) are non-monophyletic in their current composition and will need to be either abandoned or taxonomically redefined. We also identified potential cryptic species of Synalpheus in our dataset, using intraspecific and interspecific sequence variation in COI from the taxonomically well-studied S. gambarelloides group to establish a genetic divergence threshold. We then used both genetic divergence and tree-based criteria (reciprocal monophyly) to identify potential cryptic species in the remaining taxa of the genus. Our results suggest the presence of multiple cryptic lineages in Synalpheus, underlining the need for more integrative taxonomic studies-including morphological, ecological, molecular, and color pattern data-in this biologically interesting genus.

Mutualistic relationships are ubiquitous in tropical coral reefs, but the costs and benefits to partner species are often poorly known. In Caribbean coral reefs, several species of snapping shrimp (Synalpheus spp.) dwell exclusively in marine sponges, which serve as both habitat and food source. A paired experimental design was used to examine the effects of Synalpheus occupancy on predation, morphology, and growth of their sponge host Lissodendoryx colombiensis in Bocas del Toro, Panama (9.351°N, 82.258°W) in June 2009. Shrimp occupancy significantly decreased consumption of sponges by a predatory sea star (Oreaster reticulatus) and also affected sponge morphology; sponges grown without shrimps decreased in canal size, in both the laboratory and the field. Shrimp occupancy had more ambiguous effects on sponge growth. In laboratory experiments, shrimp occupancy benefited sponge growth, although all sponges experienced overall decreases in mass. In field experiments, there were no significant differences in growth between occupied and empty sponges. However, the benefits of shrimp occupancy on sponge growth were negatively correlated with overall increases in sponge size; sponges that decreased in mass during the experiment benefited more from shrimp occupancy than sponges that increased in mass. These costs and benefits suggest that Synalpheus has variable effects on sponges: positive effects on sponges in the presence of predators, and/or when sponges are decreasing in mass (e.g., during periods of physical stress), but a negative effect on sponges during periods of active sponge growth.

The present study is a preliminary report on 36 Atlantic species of the snapping shrimp genus Synalpheus Spence Bate, 1888; 32 from the western Atlantic and four from the eastern Atlantic. The vast majority of specimens were collected along the Caribbean coast of Panama between 2005 and 2008 and around São Tomé Island in 2006. Additional specimens were collected in Costa Rica, Honduras, Belize, Mexico, Dominican Republic, Aruba, Venezuela, Florida, Brazil and Cape Verde, between 1998 and 2011. Some older museum material was also examined. Three nominal varieties or subspecies, viz. S. tumidomanus africanus Crosnier & Forest, 1965, S. tumidomanus congoensis Crosnier & Forest, 1965 and S. minus var. antillensis Coutière, 1909 are elevated to full species rank, becoming S. africanus, S. congoensis, and S. antillensis, respectively. Several species are reported for the first time from Panama, Honduras, Dominican Republic, Aruba, St. Martin, and Brazil. General taxonomic and/or ecological notes are provided for all species treated herein. The need for more taxonomic and molecular work is highlighted for the western Atlantic S. cf. africanus, S. anasimus Chace, 1972, S. apioceros Coutière, 1909, S. bousfieldi Chace, 1972, S. brooksi Coutière, 1909, S. fritzmuelleri Coutière, 1909, S. goodei Coutière, 1909, S. herricki Coutière, 1909, S. cf. longicarpus (Herrick, 1891), S. ul (Ríos & Duffy, 2007) and S. yano (Ríos & Duffy, 2007), as well as the eastern Atlantic S. cf. africanus. Most species reported are illustrated in colour, some for the first time. New sponge hosts are recorded for several species of the S. gambarelloides (Nardo, 1847) group. A table summarising life habits and social organisation for all presently known Atlantic species of Synalpheus is provided. Keys for the identification of all presently known western and eastern species of Synalpheus are also provided.

When functional traits are evolutionarily conserved, phylogenetic relatedness can serve as a proxy for ecological similarity to examine whether functional differences among species mediate community assembly. Using phylogenetic- and trait-based analyses, we demonstrate that sponge-dwelling shrimp (Synalpheus) assemblages are structured by size-based habitat filtering, interacting with competitive exclusion mediated by social system. Most shrimp communities were more closely related and/or more similar in size than randomized communities, consistent with habitat filtering facilitated by phylogenetically conserved body size. Those sponges with greater space heterogeneity hosted shrimp communities with greater size diversity, corroborating the importance of size in niche use. However, communities containing eusocial shrimp - which cooperatively defend territories - were less phylogenetically related and less similar in size, suggesting that eusociality enhances competitive ability and drives competitive exclusion. Our analyses demonstrate that community assembly in this diverse system occurs via traits mediating niche use and differential competitive ability.

Sponge-dwelling snapping shrimps are often more heavily parasitized by bopyrid isopods than their free-living relatives, but little is known about how parasitism influences the be havior and morphology of these shrimps. In this study, we measured parasitism rates in the eusocial snapping shrimp Synalpheus elizabethae and tested whether parasitism by bopyrid isopods (Bopyrione sp.) affects shrimp activity levels and morphology. Using field surveys, we found that S. elizabethae suffer higher parasitism rates when inhabiting the sponge Lissodendoryx colombiensis than do co-occurring pair-forming congeners (S. yano and S. dardeaui) in the same host. In laboratory behavioral assays, parasitized S. elizabethae showed 50% lower activity levels than unparasitized colony members, suggesting that infection by bopyrids decreases shrimp activity. Finally, parasitism influenced shrimp morphology; parasitized S. elizabethae individuals were larger, but had relatively smaller major chelae (25% reduction) than unparasitized individuals. Parasites comprised ~5% of the entire body weight of an individual shrimp. Together these data suggest that parasitism by bopyrid isopods may incur significant energetic costs for commensal sponge-dwelling shrimps such as Synalpheus, and may be especially severe for social species such as S. elizabethae.

Alpheid snapping shrimp are one of the most diverse groups of coral-reef fauna, and sponge-dwelling shrimp in the genus Synalpheus (gambarelloides species group) have in particular become a model system for studying the evolution of social biology and host use in marine invertebrates. Despite recent advances in understanding the evolution and systematics of Synalpheus, the taxonomy and phylogenetic relationships within this group remain challenging. More than 20 new species in the S. gambarelloides species group have been described over the past two decades, primarily within several cryptic species complexes, which has doubled the known diversity of this group in the West Atlantic. Here we construct a new phylogenetic tree describing relationships between 40 different species from the S. gambarelloides-group (119 individuals from across the Caribbean), using a combined dataset consisting of two mitochondrial loci (16S and COI), one nuclear protein-coding gene (elongation-factor 2), and 33 morphological characters. Putative conspecific specimens of Synalpheus from multiple locations across the Caribbean were always monophyletic (with one exception), providing strong support for the validity of species concepts based on morphology. Our study also provides further evidence for the monophyly of the S. gambarelloides-group in the Caribbean, resolves the molecular relationships within many recently described species complexes, and provides a new phylogenetic framework for future evolutionary studies of this group.

Both body size and habitat architecture have pervasive effects on the form, function, and inter- actions of organisms, and can play especially impor- tant roles in structuring intimate associations between host organisms and their obligate associates. In this study, we examined how body size is related to host use in a diverse clade of closely related snapping shrimp species (Synalpheus) that live in the interior canals of sponges. Using data from an extensive survey of sponge-dwelling Synalpheus from Jamaica, we tested how sponge morphology (interior canal size and individual sponge volume) was related to the identity and diversity of Synalpheus inhabitants. In cross- species comparisons, we found a strong positive cor- relation between Synalpheus species body size and sponge host canal size, using both raw species cor- relations and phylogenetic independent contrasts. Shrimp abundance increased with sponge volume in all sponge hosts tested, and species richness increased with volume in 2 host sponge species. Despite this evi- dence for a strong constraining influence of habitat architecture on shrimp communities, simulation stud- ies demonstrated that shrimp used only a subset of appropriately sized sponges, indicating that size match- ing is not the sole determinant of sponge host use. Closely related sponges hosted more similar shrimp communities than unrelated sponges (despite moderate similarity in canal size between unrelated sponges), suggesting that additional genus-specific sponge traits also influence host use. Our study suggests multiple sponge traits likely limit Synalpheus host use, and has important implications for understanding how host use influences speciation of this diverse group.

Sixteen species of sponge-dwelling snapping shrimp in the genus Synalpheus (gambarelloides group) were collected from sites spanning the south coast of Curacao, including three new to science. Synalpheus hoetjesi sp. nov. belongs to a species complex that includes Synalpheus pandionis, S. dardeaui, S. yano, S. goodei, S. longicarpus, and S. ul. Synalpheus kuadramanus sp. nov. is a distinctive shrimp characterized by a short, square moveable finger on the major first pereopod and by brilliant turquoise embryos in females. Synalpheus orapilosus sp. nov. is a shrimp most morphologically similar to Synalpheus barahonensis—both species share the distinctive character of a tuft of setae on the distal end of the third maxilliped, instead of a distal circlet of spines—but can be distinguished from the latter by the number of carpal segments on the second pereopod. Although eusocial Synalpheus species (defined here as species that live in large colonies with strong reproductive skew) are often the most numerically abundant Synalpheus collected from sponges at other sites, only pair-bonding Synalpheus species were recorded from our collections in Curacao.

Individual variation in habitat use has important ecological and evolutionary consequences. Here, we combine developmental and functional approaches to study habitat use in Pugettia producta, a marine crab that sequesters pigments from the algae it inhabits and consumes to camouflage with different colored algal habitats. Pugettia from different habitats differ in size and color; individuals living in red intertidal algae are small and red, whereas crabs in amber-colored kelp forests are larger and more amber. We examine the developmental causes (effects of size and experience) and the functional consequences (growth and mortality rates) of size-specific habitat use in Pugettia. We demonstrate that positive preference induction may be a mechanism facilitating size-specific habitat use: prior feeding experience with kelp (in the field or laboratory) increases habitat preferences for kelp but only for larger crabs. Habitat use also has important fitness consequences; small red crabs grow equally fast on both kelp and red algae but suffer much higher mortality in kelp; large red crabs grow faster on kelp diets relative to red algae but experience only marginally higher mortality in kelp. Thus, habitat-specific mortality rates may explain the use of intertidal red algal habitats by small crabs, whereas reduced growth of large crabs on red algae may help trigger shifts to subtidal kelp habitats. Size-specific functional consequences of habitat use may select for developmental processes--such as positive preference induction--that facilitate shifts in habitat use in Pugettia and other phenotypically plastic organisms that shift habitats through ontogeny. Copyright 2010, Oxford University Press.

Twenty-two species of sponge-dwelling shrimp in the genus Synalpheus were collected in the vicinity of Discovery Bay, Jamaica. Four of these species are new to science. Synalpheus thele n. sp., S. corallinus n. sp., and S. plumosetosus n. sp. belong to a group of morphologically similar species that also includes S. brooksi, S. bousfieldi, S. carpenteri, and S. chacei. Synalpheus irie n. sp. is a highly distinctive shrimp most similar to S. mcclendoni, but can be distinguished from the latter by the unique bowl-shaped fingers of the major chela and the two-pronged distal protuberance on the palm of the major chela. Synalpheus belizensis and S. regalis are reported for the first time from outside their type localities in Belize, while S. bocas and S. duffyi are reported for the first time outside their type localities in Caribbean Panama.

Although experimental studies have demonstrated the antipredatory advantages of camouflage and its associated costs, few studies have examined the evolution of camouflage in a phylogenetic context. We use phylogenetic comparative methods to examine evolutionary trade-offs associated with camouflage in the crab superfamily Majoidea. The majoids, or spider crabs, are known for their decoration behavior in which they attach materials from their environment to hooked setae on their carapace. We found that coverage of hooked setae on a crab (morphology) strongly predicts decoration cover in the field (behavior). Half of the species examined exhibited decreases in the coverage of hooked setae with ontogeny, and we also found a strong negative correlation between the extent of hooked setae and adult body size among species using independent contrasts, suggesting that size may constrain the evolution of camouflage. Finally, using a well-resolved clade of epialtids (kelp crabs)--many of which decorate little but use color change as an alternative camouflage strategy--we found a negative correlation between utilization of decoration versus color camouflage strategies. Our findings suggest that the costs of hook production and decoration maintenance and/or the lowered adaptive value of camouflage for larger species may limit the evolutionary distribution of decoration camouflage among the majoids.

Although camouflage is a common predator defense strategy across a wide variety of organisms, direct tests of the adaptive and ecological consequences of camouflage are rare. In this study, we demonstrated that closely related crabs in the family Epialtidae coexist in the same algal environment but use alternative forms of camouflage--decoration and color change--to protect themselves from predation. Decoration and color change are both plastic camouflage strategies in that they can be changed to match different habitats: decoration occurs on a short timescale (hours to days), while color change accompanies molting and occurs on longer timescales (months). We found that the species that decorated the most had the lowest magnitude of color change (Pugettia richii); the species that decorated the least showed the highest magnitude of color change (Pugettia producta), and a third species (Mimulus foliatus) was intermediate in both decoration and color change, suggesting a negative correlation in utilization of these strategies. This negative correlation between color change and decoration camouflage utilization mirrored the effectiveness of these camouflage strategies in reducing predation in different species. Color camouflage primarily reduced predation on P. producta, while decoration camouflage (but not color camouflage) reduced predation on P. richii. These results indicate there might be among-species trade-offs in utilization and/or effectiveness of these two forms of plastic camouflage, with important consequences for distribution of these species among habitats and the evolution of different camouflage strategies in this group.

Relatively few studies have compared behavioral variation of more than one species among different locations; yet examining geographic variation in behavior in a comparative context is crucial to help elucidate the generality of geographic patterns. We studied geographic variation in decoration preferences for 2 spider crabs (Brachyura: Majoidea), Micippa platipes and Tiarinia cornigera, which co-occur in intertidal areas along the coast of Japan. Both M. platipes and T. corni- gera primarily feed on algae and use them for 'decoration' (i.e. attach them to hooked setae on their carapace). We tested whether individuals from 3 locations along the east coast of Japan differed in their decoration and consumption selectivity for certain algae in the field, and also tested decoration and consumption preferences of M. platipes in laboratory assays. At the 2 more northern locations, both species showed little selectivity among algae, primarily using them for decoration in proportion to their abundance. Conversely, at the southern location, M. platipes exhibited strong preferences for the alga Hypnea pannosa in both field and laboratory assays, and both crab species strongly avoided the alga Corallina pilulifera. Using both an overall selectivity index (SEo) and a proportional selec- tivity index (PSE) calculated for each alga, we compared algal use by the crabs vs. algal availability at the 3 locations. Both indices indicated that both species were more selective (had stronger prefer- ences or avoidances of available algae) at the southern location than at the 2 more northern locations. Potential factors driving this latitudinal gradient in selectivity include seasonal and geographic vari- ability in both decoration availability and crab decoration preferences.

Anthropogenically induced global climate change has profound implications for marine ecosystems and the economic and social systems that depend upon them. The relationship between temperature and individual performance is reasonably well understood, and much climate-related research has focused on potential shifts in distribution and abundance driven directly by temperature. However, recent work has revealed that both abiotic changes and biological responses in the ocean will be substantially more complex. For example, changes in ocean chemistry may be more important than changes in temperature for the performance and survival of many organisms. Ocean circulation, which drives larval transport, will also change, with important consequences for population dynamics. Furthermore, climatic impacts on one or a few 'leverage species' may result in sweeping community-level changes. Finally, synergistic effects between climate and other anthropogenic variables, particularly fishing pressure, will likely exacerbate climate-induced changes. Efforts to manage and conserve living marine systems in the face of climate change will require improvements to the existing predictive framework. Key directions for future research include identifying key demographic transitions that influence population dynamics, predicting changes in the community-level impacts of ecologically dominant species, incorporating populations' ability to evolve (adapt), and understanding the scales over which climate will change and living systems will respond.

Elucidating patterns and causes of interaction among mutualistic species is a major focus of ecology, and recent meta-analyses of terrestrial networks show that network-level reciprocal specialization tends to be higher in intimate mutualisms than in nonintimate mutualisms. It is largely unknown, however, whether this pattern holds for and what factors affect specialization in marine mutualisms. Here we present the first analysis of network specialization ([Formula: see text]) for marine mutualistic networks. Specialization among eight Indo-Pacific networks of obligate mutualistic gobies and shrimps was indistinguishable from that among comparably intimate terrestrial mutualisms (ants-myrmecophytes) and higher than that among nonintimate ones (seed dispersers). Specialization was affected by variability in habitat use for both gobies and shrimps and by phylogenetic history for shrimps. Habitat use was phylogenetically conserved among shrimp, and thus effects of shrimp phylogeny on partner choice were mediated in part by habitat. By contrast, habitat use and pairing patterns in gobies were not related to phylogenetic history. This asymmetry appears to result from evolutionary constraints on partner use in shrimps and convergence among distantly related gobies to utilize burrows provided by multiple shrimp species. Results indicate that the evolution of mutualism is affected by life-history characteristics that transcend environments and that different factors constrain interactions in disparate ecosystems.

What makes a community invasible? For over a century ecologists have sought to understand the relative importance of biotic and abiotic factors that determine community composition. The fact that we are still exploring this topic today hints at both its importance and complexity. As the impacts from harmful non-native species accumulate, it has become increasingly urgent to find answers to the more applied aspects of this question: what makes a habitat vulnerable to invasion by additional species, and which species are likely to invade? Answers to these questions will not only aid in targeting conservation efforts but will also advance our understanding of marine community ecology. Although the relative importance of abiotic vs. biotic factors in making a habitat invasible varies, abiotic factors undoubtedly serve as the first “filter” to invasions, limiting establishment of non-native (=exotic) species to conditions approximating their native ranges. As obvious examples, tropical corals will not establish in boreal waters, and temperate rocky intertidal species will not colonize tropical shores. Similarly, species cannot invade a community if propagules do not arrive at the site. Other chapters in this volume cover the influence of abiotic factors and propagule supply (Chap. 7, Johnston et al.; Chap. 8, Miller and Ruiz; Chap. 19, Hewitt et al.), so we only briefly review these factors. In this chapter we focus on the question of predicting invasion success of non-native species that are (1) transported to the habitat in question (i.e., propagule supply is not extremely limiting) and (2) physiologically capable of surviving in the climatic regime. We begin with the observation that even in areas of suitable habitat within the current range of an introduced species, there is often dramatic variation in the density, presence, and overall success of the invader. We seek to explain this variation in terms of processes that control the availability of resources. These include not only abiotic and physical factors that determine base resource levels, but also interactions between species or between organisms and their environment that increase resource availability (through disturbance) or decrease resource availability (through competitive processes), or create new resources (through facilitation) (Fig. 12.1).

In this study, we constructed the first molecular phylogeny of the diverse crab superfamily Majoidea (Decapoda: Pleocyemata: Brachyura), using three loci (16S, COI, and 28S) from 37 majoid species. We used this molecular phylogeny to evaluate evidence for phylogenetic hypotheses based on larval and adult morphology. Our study supports several relationships predicted from larval morphology. These include a monophyletic Oregoniidae family branching close to the base of the tree; a close phylogenetic association among the Epialtidae, Pisidae, Tychidae, and Mithracidae families; and some support for the monophyly of the Inachidae and Majidae families. However, not all majoid families were monophyletic in our molecular tree, providing weaker support for phylogenetic hypotheses inferred strictly from adult morphology (i.e., monophyly of individual families). This suggests the adult morphological characters traditionally used to classify majoids into different families may be subject to convergence. Furthermore, trees constructed with data from any single locus were more poorly resolved than trees constructed from the combined dataset, suggesting that utilization of multiple loci are necessary to reconstruct relationships in this group.

Although human-mediated extinctions disproportionately affect higher trophic levels, the ecosystem consequences of declining diversity are best known for plants and herbivores. We combined field surveys and experimental manipulations to examine the consequences of changing predator diversity for trophic cascades in kelp forests. In field surveys we found that predator diversity was negatively correlated with herbivore abundance and positively correlated with kelp abundance. To assess whether this relationship was causal, we manipulated predator richness in kelp mesocosms, and found that decreasing predator richness increased herbivore grazing, leading to a decrease in the biomass of the giant kelp Macrocystis. The presence of different predators caused different herbivores to alter their behaviour by reducing grazing, such that total grazing was lowest at highest predator diversity. Our results suggest that declining predator diversity can have cascading effects on community structure by reducing the abundance of key habitat-providing species.

Anthropogenically induced global climate change has profound implications for marine ecosystems and the economic and social systems that depend upon them. The relationship between temperature and individual performance is reasonably well understood, and much climate-related research has focused on potential shifts in distribution and abundance driven directly by temperature. However, recent work has revealed that both abiotic changes and biological responses in the ocean will be substantially more complex. For example, changes in ocean chemistry may be more important than changes in temperature for the performance and survival of many organisms. Ocean circulation, which drives larval transport, will also change, with important consequences for population dynamics. Furthermore, climatic impacts on one or a few 'leverage species' may result in sweeping community-level changes. Finally, synergistic effects between climate and other anthropogenic variables, particularly fishing pressure, will likely exacerbate climate-induced changes. Efforts to manage and conserve living marine systems in the face of climate change will require improvements to the existing predictive framework. Key directions for future research include identifying key demographic transitions that influence population dynamics, predicting changes in the community-level impacts of ecologically dominant species, incorporating populations' ability to evolve (adapt), and understanding the scales over which climate will change and living systems will respond.

The tropical shrimp genus Synalpheus includes the only eusocial marine animals. In much of the Caribbean, eusocial species have dominated the diverse fauna of sponge-dwelling shrimp in coral rubble for at least the past two decades. Here we document a recent, dramatic decline and apparent local extinction of eusocial shrimp species on the Belize Barrier Reef. Our collections from shallow reefs in central Belize in 2012 failed to locate three of the four eusocial species formerly abundant in the area, and showed steep declines in colony size and increases in frequency of queenless colonies prior to their disappearance. Concordant with these declines, several nonsocial, pair-forming Synalpheus species increased in frequency. The decline in eusocial shrimp is explained in part by disappearance of two sponge species on which they specialize. Eusocial shrimp collections from Jamaica in 2012 showed similar patterns of decline in colony size and increased queenlessness compared with prior Jamaican collections. The decline and local extinction of eusocial shrimp happened against a backdrop of changes in coral assemblages during recent decades, and may reflect changes in abundance and quality of dead coral substratum and succession of the diverse cryptic organisms living within it. These changes document potentially worrisome declines in a unique taxon of eusocial marine animals.

Sampling of eight sites along the west coast of Barbados, West Indies, yielded 14 species of sponge-dwelling shrimps in the gambarelloides group of the genus Synalpheus, including one new species described here as Synalpheus microneptunus n. sp. The new species is a member of the S. paraneptunus Coutiere species complex and is distinguished from other species in that group by the combination of four carpal segments in the second pereopod, uropodal exopod with 2 nd distolateral tooth smaller than the other two teeth and set in line with movable spine, and a small blade on the scaphocerite. Synalpheus microneptunus n. sp. is the smallest species in the complex (2.2-2.9 mm CL) and lives in small colonies, usually with fewer than 10 individuals, often with a single breeding female. Synalpheus thele Macdonald, Hultgren & Duffy is reported for the first time from outside its type locality in Jamaica. Sampling in Barbados produced fewer species than did similar efforts in Jamaica and Curacao, possibly due to the relatively isolated position of the island at the eastern (windward) edge of the Caribbean Sea.