Streambed microstructure predicts evolution of development and life history mode in the plethodontid salamander Eurycea tynerensis

Background

Habitat variation strongly influences the evolution of developmentally flexible traits, and may drive speciation and diversification. The plethodontid salamander Eurycea tynerensis is endemic to the geologically diverse Ozark Plateau of south-central North America, and comprises both strictly aquatic paedomorphic populations (achieving reproductive maturity while remaining in the larval form) and more terrestrial metamorphic populations. The switch between developmental modes has occurred many times, but populations typically exhibit a single life history mode. This unique system offers an opportunity to study the specific ecological circumstances under which alternate developmental and life history modes evolve. We use phylogenetic independent contrasts to test for relationships between a key microhabitat feature (streambed sediment) and this major life history polymorphism.

Results

We find streambed microstructure (sediment particle size, type and degree of sorting) to be highly correlated with life-history mode. Eurycea tynerensis is paedomorphic in streams containing large chert gravel, but metamorphoses in nearby streams containing poorly sorted, clastic material such as sandstone or siltstone.

Conclusion

Deposits of large chert gravel create loosely associated streambeds, which provide access to subsurface water during dry summer months. Conversely, streambeds composed of more densely packed sandstone and siltstone sediments leave no subterranean refuge when surface water dries, presumably necessitating metamorphosis and use of terrestrial habitats. This represents a clear example of the relationship between microhabitat structure and evolution of a major developmental and life history trait, and has broad implications for the role of localized ecological conditions on larger-scale evolutionary processes.     

Speciation, phylogeography and evolution of life history and morphology in plethodontid salamanders of the Eurycea multiplicata complex

Understanding the complex interactions among environment, genotype and ontogeny in determining organismal phenotypes is cental to many biological disciplines. The Eurycea multiplicata complex, endemic to the Interior Highlands (Ozark Plateau and Ouachita Mountains) of eastern North America, comprises a diverse radiation of paedomorphic surface-dwelling (E. tynerensis), metamorphic surface-dwelling (E. multiplicata multiplicata and E. m. griseogaster) and metamorphic subterranean (Typhlotriton spelaeus) hemidactyliine plethodontid salamanders. Portions of two mitochondrial genes, cytochrome-b and NADH dehydrogenase-4, totalling 1818 base pairs (bp) were sequenced for 70 ingroup individuals plus numerous outgroup taxa, to examine the biogeography and relationships among these morphologically disparate species. Results show the E. multiplicata complex to be monophyletic, with its two most divergent clades corresponding to geography, not morphology or life history. Transforming surface-dwelling populations from the Ouachitas (E. m. multiplicata) are sister to the Ozark taxa, including paedomorphic surface-dwelling (E. tynerensis), subterranean (T. spelaeus) and transforming surface-dwelling salamanders assigned to the 'subspecies'E. m. griseogaster. Among Ozark taxa T. spelaeus (deeply nested within Eurycea) is sister to a clade that includes E. m. griseogaster and E. tynerensis. Current taxonomy suggests that paedomorphic populations (E. tynerensis) from the western Ozarks are distinct from nearby transforming populations (E. m. griseogaster). However, paedomorphic and transforming salamanders do not form reciprocally monophyletic groups and many populations share almost identical haplotypes. Ancestral state reconstruction of life history traits shows that paedomorphosis arose independently from three to nine times. Most populations are either completely paedomorphic or completely transforming. This suggests that local habitat parameters strongly influence life history mode in this complex, either facultatively or by selection for particular genotypes.     

River islands,refugia and genetic structuring in the endemic brown frog Rana kukunoris (Anura,Ranidae) of the Qinghai‐Tibetan Plateau

Frequently, Pleistocene climatic cycling has been found to be the diver of genetic structuring in populations, even in areas that did not have continental ice sheets, such as on the Qinghai‐Tibetan Plateau (QTP). Typically, species distributed on the plateau have been hypothesized to re‐treat to south‐eastern refugia, especially during the Last Glacial Maximum (LGM). We evaluated sequence variation in the mitochondrial DNA gene Cytb and the nuclear DNA gene RAG‐1 in Rana kukunoris, a species endemic to the QTP. Two major lineages, N and S, were identified, and lineage N was further subdivided into N1 and N2. The geographical distribution and genealogical divergences supported the hypothesis of multiple refugia. However, major lineages and sublineages diverged prior to the LGM. Demographical expansion was detected only in lineage S and sublineage N2. Sublineage N1 might have survived several glacial cycles in situ and did not expand after the LGM because of the absence of suitable habitat; it survived in river islands. Genetic analysis and environment modelling suggested that the north‐eastern edge of QTP contained a major refugium for R. kukunoris. From here, lineage S dispersed southwards after the LGM. Two microrefugia in northern Qilian Mountains greatly contributed to current level of intraspecific genetic diversity. These results were found to have important implications for the habitat conservation in Northwest China.     

Thyroid hormone responsive QTL and the evolution of paedomorphic salamanders

The transformation of ancestral phenotypes into novel traits is poorly understood for many examples of evolutionary novelty. Ancestrally, salamanders have a biphasic life cycle with an aquatic larval stage, a brief and pronounced metamorphosis, followed by a terrestrial adult stage. Repeatedly during evolution, metamorphic timing has been delayed to exploit growth-permissive environments, resulting in paedomorphic salamanders that retain larval traits as adults. We used thyroid hormone (TH) to rescue metamorphic phenotypes in paedomorphic salamanders and then identified quantitative trait loci (QTL) for life history traits that are associated with amphibian life cycle evolution: metamorphic timing and adult body size. We demonstrate that paedomorphic tiger salamanders (Ambystoma tigrinum complex) carry alleles at three moderate effect QTL (met1–3) that vary in responsiveness to TH and additively affect metamorphic timing. Salamanders that delay metamorphosis attain significantly larger body sizes as adults and met2 explains a significant portion of this variation. Thus, substitution of alleles at TH-responsive loci suggests an adaptive pleiotropic basis for two key life-history traits in amphibians: body size and metamorphic timing. Our study demonstrates a likely pathway for the evolution of novel paedomorphic species from metamorphic ancestors via selection of TH-response alleles that delay metamorphic timing and increase adult body size.     

Colonization history of the Japanese water shrewChimarrogale platycephala, in the Japanese Islands

To evaluate the intraspecific evolutionary history and local differentiation of the Japanese water shrewChimarrogale platycephala (Temminck, 1842), we an a lyzed the mitochondrial cytochromeb (Cytb) sequence divergence for samples from 55 localities in the Japanese is lands of Honshu and Kyushu. According to phylogenetic trees based on theCytb data, there were fourCytb haplotype lineages, which showed rough affinities with geographic areas, namely, Eastern/Central Honshu, the Kinki District of Western Honshu, the Chugoku District of Western Honshu, and Kyushu. However, in the alpine areas of the boundary between the Kinki and Chugoku Districts, complicated distribution patterns of theCytb haplotypes were revealed. Considering the present data and geological history in the Quaternary, we hypothesized the following evolutionary scenario. First, differ entiation and division into four primary ancestral geographic colonies of the shrews occurred in hypothetical refugia in the mid — late Pleistocene. Subsequently, rapid expansion occurred and caused the complicated distribution patterns of theCytb haplotypes in the boundary areas owing to the complex topography during the late stage of the Quaternary.     

Asymmetric reproductive isolation among polymorphic salamanders

The study of reproductive isolation (RI) as a prerequisite to sympatric speciation has been limited by a focus on species that have already experienced isolation. However, a complete understanding of speciation depends on observing taxa before they complete the speciation process. We estimated RI in field populations of the polyphenic mole salamander, Ambystoma talpoideum, by capturing paedomorphic (aquatic) and metamorphic (terrestrial) adults during the breeding season from two natural populations. We found evidence for asymmetric RI between morphs, such that paedomorphic males and metamorphic females had functionally zero RI, whereas metamorphic males and paedomorphic females had substantial RI. Evidence suggests that ecological factors such as the abundance of each morph, timing of rainfall, and water depth of the breeding habitat play a large role in the production of these asymmetries. Spatial aspects of RI had a greater relative impact on overall isolation than temporal differences, in part because metamorphic adults were often captured in shallower water than paedomorphic adults. However, morph separation varied across populations and year, suggesting that environmental heterogeneity likely plays a large role in the potential for RI, particularly between metamorphic males and paedomorphic females. In addition, body‐size variation and behavioural differences could also influence the RI estimates presented here. Although facultative paedomorphosis appears to have played a large role in macroevolutionary change via allopatric speciation in some taxa, our results suggest that there is little potential for sympatric speciation in the future within these populations. However, asymmetric RI creates the opportunity for fitness differences between morphs and sexes that would directly affect the maintenance of this polymorphism. Our results suggest that further studies on this and other polyphenisms may provide valuable insight into the evolution of RI and the role of environmental heterogeneity in the production and maintenance of biological diversity. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86 , 265?281.     

Y‐chromosome evidence supports widespread signatures of three‐species Canis hybridization in eastern North America

There has been considerable discussion on the origin of the red wolf and eastern wolf and their evolution independent of the gray wolf. We analyzed mitochondrial DNA (mtDNA) and a Y‐chromosome intron sequence in combination with Y‐chromosome microsatellites from wolves and coyotes within the range of extensive wolf–coyote hybridization, that is, eastern North America. The detection of divergent Y‐chromosome haplotypes in the historic range of the eastern wolf is concordant with earlier mtDNA findings, and the absence of these haplotypes in western coyotes supports the existence of the North American evolved eastern wolf (Canis lycaon). Having haplotypes observed exclusively in eastern North America as a result of insufficient sampling in the historic range of the coyote or that these lineages subsequently went extinct in western geographies is unlikely given that eastern‐specific mtDNA and Y‐chromosome haplotypes represent lineages divergent from those observed in extant western coyotes. By combining Y‐chromosome and mtDNA distributional patterns, we identified hybrid genomes of eastern wolf, coyote, gray wolf, and potentially dog origin in Canis populations of central and eastern North America. The natural contemporary eastern Canis populations represent an important example of widespread introgression resulting in hybrid genomes across the original C. lycaon range that appears to be facilitated by the eastern wolf acting as a conduit for hybridization. Applying conventional taxonomic nomenclature and species‐based conservation initiatives, particularly in human‐modified landscapes, may be counterproductive to the effective management of these hybrids and fails to consider their evolutionary potential.     

Cryptic divergent lineages of Pultenaea pauciflora M.B. Scott (Fabaceae: Mirbelieae) exhibit different evolutionary history

Genetic structure among disjunct population groups of Pultenaea pauciflora was assessed to determine the evolutionary history of this species as a basis for conservation management strategies. Analysis of individuals from all extant populations using 1737 amplified length polymorphism markers revealed two highly divergent genetic entities with strong geographical structuring. Populations located at Narrogin and Brookton clustered together in Bayesian assignment analysis with every individual optimally placed in a single cluster with complete membership. Genetic differentiation between populations in these two areas was very low. Populations at Boddington were highly divergent from those located at Narrogin and Brookton. All individuals from Boddington populations were optimally placed into a second cluster with complete membership. Populations located at Boddington maintain lower levels of allelic diversity, yet greater levels of mean heterozygosity than populations located at Narrogin and Brookton. The degree of genetic differentiation and different patterns of genetic diversity strongly suggest historical divergence and separate evolutionary influences on the two lineages that occur in different ecological habitat. These Evolutionary Significant Units are likely to represent two cryptic sister taxa in the extant populations currently recognized as P. pauciflora, and the reassessment of taxonomic and conservation status of both lineages is required. © 2013 State of Western Australia. Biological Journal of the Linnean Society © 2013 The Linnean Society of London     

Three deeply divided lineages of the freshwater mussel genus <Emphasis Type="Italic">Anodonta</Emphasis> in western North America

The surprising diversity and recent dramatic decline of freshwater mussels in North America have been well documented, although inventory efforts to date have been concentrated in the eastern United States. Unlike their eastern counterparts, western freshwater mussels have received comparatively little attention. The accurate identity of western lineages is a necessary component for future inventory, monitoring, and ecological work involving these taxa. Here we initiate a study involving the most speciose genus (Anodonta) in western North America, incorporating information about type localities and type specimen morphology and describing the discovery of three highly divergent lineages among four western Anodonta species. In a limited phylogenetic analysis, we find (1) that A. californiensis/nuttalliana and A.oregonensis/kennerlyi are distinct, highly divergent clades, and (2) that A. beringiana is more closely allied with A. woodiana, an Asian species, than either of the other two western North American clades. We were largely unable to resolve the placement of these three clades with respect to other anodontines, and suggest the need for a broader phylogenetic framework. We recommend, however, that the existence of these three deeply divergent groups be considered in the development of regional monitoring, conservation and research plans despite the taxonomic uncertainty.     

Genetic structure,diversity and distribution of a threatened lizard affected by widespread habitat fragmentation

Understanding the demographic consequences of habitat loss on populations is essential for the conservation of threatened species. The threatened swamp skink (Lissolepis coventryi) is restricted to fragmented wetland habitats in Victoria and southeast South Australia. It has experienced significant habitat loss in the last 150 years, particularly around the Melbourne metropolitan area, where several small and isolated populations remain. Using mtDNA and nuDNA SNPs, we examined distribution patterns and population structure to infer evolutionary history and genetic distinctiveness of populations throughout the species’ range. For populations in the Melbourne metropolitan area, we examined genetic diversity. We found the species to be highly divergent, separating into two distinct lineages to the east and west of Melbourne, likely due to geological and climate influences causing isolation of populations. Species’ detectability was low, particularly in the far east despite relatively intact habitat and presumed higher abundance. Melbourne populations showed signs of limited genetic diversity. We suggest that translocations to promote gene diversity amongst these populations, together with habitat restoration and protection, present an important management strategy for L. coventryi.

     

EVOLUTION OF PAEDOMORPHOSIS IN PLETHODONTID SALAMANDERS: ECOLOGICAL CORRELATES AND RE‐EVOLUTION OF METAMORPHOSIS

Life‐history modes can profoundly impact the biology of a species, and a classic example is the dichotomy between metamorphic (biphasic) and paedomorphic (permanently aquatic) life‐history strategies in salamanders. However, despite centuries of research on this system, several basic questions about the evolution of paedomorphosis in salamanders have not been addressed. Here, we use a nearly comprehensive, time‐calibrated phylogeny of spelerpine plethodontids to reconstruct the evolution of paedomorphosis and to test if paedomorphosis is (1) reversible; (2) associated with living in caves; (3) associated with relatively dry climatic conditions on the surface; and (4) correlated with limited range size and geographic dispersal. We find that paedomorphosis arose multiple times in spelerpines. We also find evidence for re‐evolution of metamorphosis after several million years of paedomorphosis in a lineage of Eurycea from the Edwards Plateau region of Texas. We also show for the first time using phylogenetic comparative methods that paedomorphosis is highly correlated with cave‐dwelling, arid surface environments, and small geographic range sizes, providing insights into both the causes and consequences of this major life history transition.     

Evolution and maintenance of divergent lineages in an endangered freshwater fish, <Emphasis Type="Italic">Macquaria australasica</Emphasis>

Variable hydrological regimes and habitat availability are factors that affect the distribution of freshwater dependent species and are expected to influence their levels of genetic diversity. Although geologically relatively stable, the south eastern region of Australia has experienced significant changes in hydrological conditions during the Quaternary. This area has also been recently affected by anthropogenic activities, resulting in dramatic population declines of Macquarie Perch (Macquaria australasica). We conducted a range-wide phylogeographic study of this endangered fish to assess the relationship between landscape and freshwater fish evolution in south eastern Australia and infer levels of genetic diversity and population structure. Surprisingly, we detected high genetic diversity, with 46 mtDNA control region haplotypes found across 37 sampling locations. Some lineages were remarkably divergent; one represents a putative undescribed species that probably went extinct during the period of this study. Our reconstruction of population history using a combination of coalescent and phylogenetic methods indicates that the species originated on the coast, east of the Great Dividing Range (GDR), with subsequent colonisation of the Murray-Darling basin, west of the GDR. Nested clade and IM analyses inferred a series of range expansions and fragmentations across the species range consistent with the history of climatic oscillations in south eastern Australia during the Pleistocene. We conclude that the unexpected high levels of diversity and divergence observed in M. australasica may be due to specific habitat requirements, localised recruitment, and Pleistocene climate fluctuations. Under expectations of a drier climate and increased sea levels due to global warming, populations of this and other freshwater species may be expected to experience increased habitat fragmentation and loss of genetic diversity. Conservation management should focus on habitat protection, the maintenance of genetic diversity and taxonomic review.     

Diversification across major biogeographic breaks in the African Shining/Square‐tailed Drongos complex (Passeriformes: Dicruridae)

Surprisingly, little is known about the extent of genetic structure within widely distributed and polytypic African species that are not restricted to a particular habitat type. The few studies that have been conducted suggested that speciation among African vertebrates may be intrinsically tied to habitat and the dynamic nature of biome boundaries. In the present study, we assessed the geographic structure of genetic variation across two sister‐species of drongos, the Square‐tailed Drongo (Dicrurus ludwigii) and the Shining Drongo (D. atripennis), that are distributed across multiple sub‐Saharan biogeographic regions and habitat types. Our results indicate that D. ludwigii consists of two strongly divergent lineages, corresponding to an eastern–southern lineage and a central‐western lineage. Furthermore, the central‐western lineage may be more closely related to D. atripennis, a species restricted to the Guineo‐Congolian forest block, and it should therefore be ranked as a separate species from the eastern–southern lineage. Genetic structure is also recovered within the three primary lineages of the D. atripennis–D. ludwigii complex, suggesting that the true species diversity still remains underestimated. Additional sampling and data are required to resolve the taxonomic status of several further populations. Overall, our results suggest the occurrence of complex diversification patterns across habitat types and biogeographic regions in sub‐Saharan Africa birds.     

Uplift-driven diversification revealed by the historical biogeography of the cockroach Cryptocercus Scudder (Blattodea: Cryptocercidae) in eastern Asia

Cryptocercus Scudder is a genus of wingless cockroaches, which spend their lives feeding within rotting wood in old-growth montane forests. Their dispersal capability is likely to be limited because they depend on the succession of temperate forests, but their distribution exhibits intercontinental disjunctions. Although the natural history and conservation biology of the North American species of the genus have received much attention, the evolution of the eastern Asian lineages remains enigmatic. To resolve the geographic patterns and evolutionary history of Cryptocercus in eastern Asia, we analysed genetic data of species from China (27 species), Korea (one species) and the Russian Far East (one species). We performed phylogenetic analyses of seven genes to infer the evolutionary relationships among species of Asian Cryptocercus. We then used Bayesian molecular dating to estimate the evolutionary timescale of the genus. Ancestral geographic distributions were reconstructed in rasp using statistical dispersal-vicariance analysis and statistical dispersal-extinction-cladogenesis. Our maximum-likelihood and Bayesian phylogenetic trees supported four major lineages of Cryptocercus, revealing a clear geographical pattern. The divergence of American and Asian lineages was inferred to have occurred 74.8 Ma (95% credibility interval: 51.1–103.8 Ma), with the diversification of Asian taxa beginning at 30.7 Ma (95% credibility interval: 22.9–40.3 Ma). The most recent common ancestor of Asian Cryptocercus taxa was inferred to have had a broad distribution in Asia. The uplift of the Qinghai-Tibet Plateau in the Palaeogene and Neogene, along with climatic oscillations in the Quaternary, probably had substantial effects on the formation of the disjunction pattern in the Cryptocercus lineages found in the Hengduan Mountains and Qin-Daba Mountains of China. We propose that the distribution of Cryptocercus has been strongly influenced by habitat fragmentation and subsequent allopatric speciation.     

Comparative phylogeography and population genetics within Buteo lineatus reveals evidence of distinct evolutionary lineages

Traditional subspecies classifications may suggest phylogenetic relationships that are discordant with evolutionary history and mislead evolutionary inference. To more accurately describe evolutionary relationships and inform conservation efforts, we investigated the genetic relationships and demographic histories of Buteo lineatus subspecies in eastern and western North America using 21 nuclear microsatellite loci and 375-base pairs of mitochondrial control region sequence. Frequency based analyses of mitochondrial sequence data support significant population distinction between eastern (B. l. lineatus/alleni/texanus) and western (B. l. elegans) subspecies of B. lineatus. This distinction was further supported by frequency and Bayesian analyses of the microsatellite data. We found evidence of differing demographic histories between regions; among eastern sites, mitochondrial data suggested that rapid population expansion occurred following the end of the last glacial maximum, with B. l. texanus population expansion preceding that of B. l. lineatus/alleni. No evidence of post-glacial population expansion was detected among western samples (B. l. elegans). Rather, microsatellite data suggest that the western population has experienced a recent bottleneck, presumably associated with extensive anthropogenic habitat loss during the 19th and 20th centuries. Our data indicate that eastern and western populations of B. lineatus are genetically distinct lineages, have experienced very different demographic histories, and suggest management as separate conservation units may be warranted.     

Mitochondrial DNA phylogeny of North American field crickets: perspectives on the evolution of life cycles,songs, and habitat associations

North American field crickets (genus Gryllus) exhibit a diversity of life cycles, habitat associations, and calling songs. However, patterns of evolution for these ecological and behavioral traits remain uncertain in the absence of a robust phylogenetic framework. Analyses of morphological variation have provided few clues about species relationships in the genus Gryllus. Here we use comparisons of mitochondrial DNA restriction site maps for 29 individuals representing 11 species (including potential outgroups) to examine relationships among eastern North American field crickets. Initially chosen as likely outgroup taxa, the two European species of Gryllus do not obviously fall outside of an exclusively North American clade and (based on amount of sequence divergence) appear to have diverged from North American lineages at about the same time that major North American lineages diverged from each other. The egg-overwintering crickets comprise a strongly supported monophyletic group, but relationships among these three closely related species cannot be resolved. The mtDNA data are consistent with a single origin of egg diapause and do not support a model of recent life cycle divergence and allochronic speciation for Gryllus pennsylvanicus and G. veletis. The two crickets are not sister species, despite remarkable similarity in morphology, habitat, and calling song. This conclusion is consistent with published data on allozyme variation in North American field crickets. The habitat associations of eastern North American field crickets have been labile, but calling songs sometimes have remained virtually unchanged across multiple speciation events.     

Cytochrome b Genetic Diversity and Maternal Origin of Chinese Domestic Donkey

To clarify the origin of Chinese domestic donkeys, we investigated the mitochondrial Cytb gene from 244 animals from 13 native breeds. We found 55 variable sites in the Cytb gene sequence and subsequently defined 58 haplotypes. Analysis of haplotypes in combination with Cytb sequences revealed two mitochondrial origins in Chinese domestic donkeys, phenotypically expressed by the Somalian and Nubian lineages. The Somalian lineage predominated in Chinese domestic donkey breeds. Five specific Cytb gene SNPs diagnostic of each of the lineages were found in this study: 225(T-C), 237(C-T), 915(C-T), 1014(C-T), and 1134(A-G) mutations. They effectively distinguish the Nubian from the Somalian lineage in the mtDNA Cytb gene. Both lineages are from Africa and thus support the African maternal origins of Chinese domestic donkeys. No obvious geographic structure was found in Chinese domestic donkey breeds, but the population showed abundant genetic diversity.     

Evolutionary insights into the North American Necturus beyeri complex (Amphibia: Caudata) based on molecular genetic and morphological analyses

Necturus beyeri (Caudata: Proteidae), as conceived by some, contains paedomorphic salamanders distributed from the Ochlockonee drainage of Florida to the Angelina drainage of Texas. Because these salamanders differ in color pattern and karyotype across their geographic range, we performed a phylogeographic analysis that included representatives from all major drainages as well as of all congeners. The mitochondrially encoded ND2 gene was used to infer phylogenetic relationships using Bayesian inference. Morphometrics of head shape were analyzed and included as an independent data set. Our work suggests that Necturus comprises 11 lineages. A basal split within the genus separates an ancestor of two Atlantic Coastal Plain species (Necturus lewisi and Necturus punctatus) from the ancestor of nine distinct Gulf Coastal Plain lineages. One lineage is consistent with Necturus alabamensis, a species currently recognized in the Black Warrior drainage of Alabama. Two lineages comprise Necturus maculosus, as historically recognized, and six lineages comprise N. beyeri, as recognized by some, each of which occupies a unique drainage. Both of these species are demonstrated to be paraphyletic. Head morphometrics show the same patterns as the mtDNA. Overall, lineages within Necturus exhibit an east‐to‐west progression of appearance on the phylogenetic trees. This pattern corroborates biogeographic hypotheses based on previous karyological work. Within N. beyeri, this progression separates a pattern class of two eastern lineages lacking bold spotting and possessing relatively small mean body lengths from a pattern class of four western lineages possessing bold spotting and larger mean body sizes. Thus, the two eastern lineages of N. beyeri are similar in color pattern and body size to N. punctatus either through retention of the ancestral color pattern and size for the genus or through convergent selection in eastern streams of the Gulf Coastal Plain.     

Historical Ecology, Responses to Current Ecological Changes and Conservation of Australian Spiders

In response to geohistorical events from the Mesozoic through the Tertiary with contraction of mesic forest to southwestern and eastern montane and coastal regions, and expansion of woodlands and xeric shrublands, nobreak Australian spiders today comprise relict families and genera (confined to Gondwanan habitats and refuges) along with later evolved representatives which have adapted to changing environments. Tropical relicts also persist in refugia in the arid interior while some spiders (both mygalomorphs and araneomorphs) have adapted to arid conditions, mainly through specialized behaviours. Although fire has become increasingly a phenomenon of the Australian environment it is doubtful whether any spiders are adapted to fire per se. European settlement has impacted differentially on relictual and later evolved representatives; a few species, including the funnelweb (Atrax robustus) and redback spider (Latrodectus hasselti) have benefited through enhanced habitat opportunities and some species of Badumna and other genera have become synanthropic. It is suggested that conservation strategies need to consider the ecoevolutionary history of particular spiders and their natural vulnerability or resilience to environmental factors.     

Polymorphic microsatellite markers for Mexican salamanders of the genus Ambystoma

We screened a partial genomic library enriched for microsatellites and characterized nine loci for the Mexican species of Ambystoma for studies of population structure. We tested marker variability in two metamorphic (A. granulosum, A. altamirani) and two paedomorphic (A. andersoni, A. mexicanum) species of the A. tigrinum complex. Our microsatellites were developed from pooled genomic DNA from three species, and may work on all species in the A. tigrinum complex in Mexico. These markers will be important for studies of conservation genetics in this radiation.