Search

Morphological data are a conduit for the recognition and description of species, and their acquisition has recently been broadened by geometric morphometric (GM) approaches that co-join the collection of digital data with exploratory ‘big data’ analytics. We employed this approach to dissect the Western Rattlesnake (Crotalus viridis) species-complex in North America, currently partitioned by mitochondrial (mt)DNA analyses into eastern and western lineages (two and seven subspecies, respectively). The GM data (i.e., 33 dorsal and 50 lateral head landmarks) were gleaned from 2,824 individuals located in 10 museum collections. We also downloaded and concatenated sequences for six mtDNA genes from the NCBI GenBank database. GM analyses revealed significant head shape differences attributable to size and subspecies-designation (but not their interactions). Pairwise shape distances among subspecies were significantly greater than those derived from ancestral character states via squared-change parsimony, with the greatest differences separating those most closely related. This, in turn, suggests the potential for historic character displacement as a diversifying force in the complex. All subspecies, save one, were significantly differentiated in a Bayesian discriminant function analysis (DFA), regardless of whether our priors were uniform or informative (i.e., mtDNA data). Finally, shape differences among sister-clades were significantly greater than expected by chance alone under a Brownian model of evolution, promoting the hypothesis that selection rather than drift was the driving force in the evolution of the complex. Lastly, we combine head shape and mtDNA data so as to derived an integrative taxonomy that produced robust boundaries for six OTUs (operational taxonomic units) of the C. viridis complex. We suggest these boundaries are concomitant with species-status and subsequently provide a relevant nomenclature for its recognition and representation. [ABSTRACT FROM AUTHOR]

Global climate change is apparent within the Arctic and the south-western deserts of North America, with record drought in the latter reflected within 640 000 km2 of the Colorado River Basin. To discern the manner by which natural and anthropogenic drivers have compressed Basin-wide fish biodiversity, and to establish a baseline for future climate effects, the Stream Hierarchy Model ( SHM) was employed to juxtapose fluvial topography against molecular diversities of 1092 Bluehead Sucker ( Catostomus discobolus). Mt DNA revealed three geomorphically defined evolutionarily significant units ( ESUs): Bonneville Basin, upper Little Colorado River and the remaining Colorado River Basin. Microsatellite analyses (16 loci) reinforced distinctiveness of the Bonneville Basin and upper Little Colorado River, but subdivided the Colorado River Basin into seven management units ( MUs). One represents a cline of three admixed gene pools comprising the mainstem and its lower-gradient tributaries. Six others are not only distinct genetically but also demographically (i.e. migrants/generation <9.7%). Two of these (i.e. Grand Canyon and Canyon de Chelly) are defined by geomorphology, two others (i.e. Fremont- Muddy and San Raphael rivers) are isolated by sharp declivities as they drop precipitously from the west slope into the mainstem Colorado/ Green rivers, another represents an isolated impoundment (i.e. Ringdahl Reservoir), while the last corresponds to a recognized subspecies (i.e. Zuni River, NM). Historical legacies of endemic fishes ( ESUs) and their evolutionary potential ( MUs) are clearly represented in our data, yet their arbiter will be the unrelenting natural and anthropogenic water depletions that will precipitate yet another conservation conflict within this unique but arid region. [ABSTRACT FROM AUTHOR]

Several geographically distinct mitochondrial DNA (mtDNA) lineages of the big brown bat (Eptesicus fuscus) have been documented in North America. Individuals from 2 of these lineages, an eastern and a western form, co-occur within maternity colonies in Colorado. The discovery of 2 divergent mtDNA lineages in sympatry prompted a set of questions regarding possible biological differences between haplotypes. We captured big brown bats at maternity roosts in Colorado and recorded data on body size, pelage color, litter size, roosting and overwintering behaviors, and local distributions. Wing biopsies were collected for genetic analysis. The ND2 region of the mtDNA molecule was used to determine lineage of the bats. In addition, nuclear DNA (nDNA) intron 1 of the β-globin gene was used to determine if mtDNA lineages are hybridizing. Eastern and western mtDNA lineages differed by 10.3% sequence divergence and examination of genetic data suggests recent population expansion for both lineages. Differences in distribution occur along the Colorado Front Range, with an increasing proportion of western haplotypes farther south. Results from nDNA analyses demonstrated hybridization between the 2 lineages. Additionally, no outstanding distinctiveness was found between the mtDNA lineages in natural history characters examined. We speculate that historical climate changes separated this species into isolated eastern and western populations, and that secondary contact with subsequent interbreeding was facilitated by European settlement. [ABSTRACT FROM AUTHOR]

During Pleistocene, the Laurentide ice sheet rearranged and diversified biotic distributions in eastern North America, yet had minimal physical impact in western North America where lineage diversification is instead hypothesized to result from climatic changes. If Pleistocene climatic fluctuations impacted desert species, the latter would reflect patterns of restricted gene flow concomitant with indications of demographic bottlenecks. Accordingly, molecular evidence for refugia should be present within these distributions and for subsequent range expansions as conditions improved. We sought answers to these questions by evaluating mitochondrial DNA (mtDNA) sequences from four species of rattlesnakes [ Crotalus mitchellii (speckled rattlesnake), Crotalus cerastes (sidewinder), Crotalus tigris (tiger rattlesnake), Crotalus ruber (red diamond rattlesnake)] with distributions restricted to desert regions of southwestern North America. We inferred relationships using parsimony and maximum likelihood, tested intraspecific clades for population expansions, applied an isolation-with-migration model to determine bi-directional migration rates ( m) among regions, and inferred divergence times for species and clades by applying a semiparametric penalized likelihood approach to our molecular data. Evidence for significant range expansion was present in two of eight regions in two species ( Crotalus mitchellii pyrrhus, C. tigris region north). Two species ( C. cerastes, C. mitchellii) showed a distribution concomitant with northward displacement of Baja California from mainland México, followed by vicariant separation into subclades. Effects of Pleistocene climate fluctuations were found in the distributions of all four species. Three regional diversification patterns were identified: (i) shallow genetic diversity that resulted from Pleistocene climatic events ( C. tigris, C. ruber); (ii) deep Pleistocene divisions indicating allopatric segregation of subclades within refugia ( C. mitchellii, C. cerastes); and (iii) lineage diversifications that extended to Pliocene or Late Miocene ( C. mitchellii, C. cerastes). Clade-diversifying and clade-constraining effects impacted the four species of rattlesnakes unequally. We found relatively high levels of molecular diversification in the two most broadly distributed species ( C. mitchellii, C. cerastes), and lower levels of genetic diversification in the two species ( C. tigris, C. ruber) whose ranges are relatively more restricted. Furthermore, in several cases, the distributions of subspecies were not congruent with our molecular information. We suggest regional conservation perspectives for southwestern deserts cannot rely upon subspecies as biodiversity surrogates, but must instead employ a molecular and deep historical perspective as a primary mechanism to frame biodiversity reserves within this region. [ABSTRACT FROM AUTHOR]

Summary 1. Fishes can often rebound numerically and distributionally from short-term (i.e. seasonal) drought, yet their capacity to recover from decades or centuries of drought is less apparent. An exceedingly warm and dry period swept the intermontane west of North America ca. 7500 years BP, concomitant with an abrupt extinction of >35 mammal species. Were larger fishes in mainstem rivers also impacted by this drought? 2. The Colorado River Basin encompasses seven states in western North America and drains 600 000 km2 . Its endemic mainstem fish community is ancient (i.e. Miocene) but depauperate. 3. We evaluated one widely distributed candidate species (flannelmouth sucker, Catostomus latipinnis ) for basin-wide genetic and geographic structure at three fast-evolving mitochondrial (mt) DNA genes, ND2 with 589 bp and ATPase 8 and 6 with 642 bp. It is hypothesized that a concomitant signature would be present in the mtDNA of this species, if indeed it had been seriously bottlenecked by post-Pleistocene drought. A total of 352 individuals were sequenced from 24 populations (4–40 individuals/population; average of 14.7). 4. Only 49 unique haplotypes were found, 53% of which represented single individuals. Haplotype diversity was high (0.905 ± 0.007) whereas nucleotide diversity was low (0.002 ± 0.000). 5. A significant and positive geographical cline (P < 0.001) in nucleotide diversity was observed as sampling locations progressed upstream from southwest to northeast. These results divided the Colorado River Basin into three reaches: the lower reach with six populations and 83 individuals; the upper reach with seven populations and 83 individuals; and the middle reach with 11 populations and 186 individuals. An analysis of molecular variance (amova) revealed that 81.5% of the total genetic variation was within populations, 16% among populations within reaches and 2.5% among reaches. Only the last was significant. Populations from the... [ABSTRACT FROM AUTHOR]

Recent molecular evidence suggests that at least eight species of bonefishes (Albuliformes: Albulidae: Albula) are found worldwide (Colborn et al. 2001). Adults of most of these species, including two that are restricted to the eastern Pacific Ocean (Albula sp. A from the Gulf of California and Albula sp. C from the Gulf of Panama), have not been formally described. Because cryptic species of bonefishes are known to occur sympatrically, population genetics data provide an important tool for taxonomic studies on this group. Isozyme analyses conducted on larval, juvenile and adult bonefish from the Guaymas region of the central Gulf of California confirmed that only a single species (Albula sp. A) was present there. In addition, analysis of a segment of the cytochrome b gene from three adult Albula collected from coastal waters of southern California revealed high sequence homology with Albula sp. A, suggesting that the southern California specimens were conspecific with those from Guaymas. However, the southern distributional limit of Albula sp. A, and whether there are regions where Albula sp. A and C occur sympatrically, are unknown. The historical background of the available name Atopichthysesunculus Garman, 1899 [= Albula esuncula (Garman, 1899)], and problems associated with the nomenclature of the two species of eastern Pacific bonefishes, are summarized. The systematic status of the related shafted bonefish, Dixonina (= Albula) nemoptera Fowler, 1911, is also reviewed. [ABSTRACT FROM AUTHOR]