Symposium: Biogeography & Diversification of Amphibians & Reptiles - Pacific Northwest & CA Floristic Province IIRoom: Ballroom 111B2022-07-30 10:00 - 12:00 |
| Moderator: Chris Feldman |
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1. 10:00 Plethodontid Salamander Species Formation and Lineage Boundaries within California’s North Coast Ranges and the Klamath Mountains. Sean Reilly*, University of California sreilly@ucsc.edu
The Coast Ranges and Klamath Mountains of northern California are rugged and contain a mosaic of habitats and microclimates influenced by clinal patterns of rainfall and temperature from south to north and from west to east. This dynamic interaction of abiotic forces is not constant and has fluctuated greatly since the Pliocene. Historical processes such as mountain formation and plate tectonics have also been prevalent during this time period and have influenced lineage boundaries across a wide range of plants and animals, particularly for low vagility terrestrial vertebrates such as plethodontid salamanders. Here I will discuss some of the phylogeographic work done by myself and others before me on plethodontid salamander diversification in this dynamic and fascinating region. |
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2. 10:15 Aridification and the Diversification of Slender Salamanders (genus Batrachoseps) in Western North America. Elizabeth Jockusch*, University of Connecticut elizabeth.jockusch@uconn.edu
Slender salamanders (genus Batrachoseps) form the most species-rich amphibian radiation in western North America, a region they have occupied for nearly 40 million years. This time period has been marked by large-scale geological, ecological, and climatic changes. Genetic data suggest that Batrachoseps has persisted in situ through these changes, with extensive diversification since the mid-Miocene. This in situ diversification contrasts with the expectation of niche-tracking resulting in range shifts under climate change, as observed in many other taxa. This difference in response is explained by the natural history of Batrachoseps. Minimalist needs, stemming in part from its fully terrestrial life cycle, confer persistence superpowers. In combination with the low vagility of Batrachoseps and its long-term presence within the region, this ability to persist underlies the following phenomena observed in the genetic data: high levels of geographic structuring throughout the range of the genus; high genetic diversity at dry range fringes; isolated populations in deserts and other seemingly inhospitable habitats; and evidence for repeated instances of secondary contact followed by gene flow. The regularity with which divergent lineages of Batrachoseps have been discovered, even in well-sampled regions, points to the value of continued exploration, especially in isolated, mesic pockets of habitat. |
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3. 10:30 Against “Speciation”: David Wake on Species and the Biogeography of the Salamander Ring SpeciesEnsatina eschscholtzii. Shawn Kuchta*, Ohio University kuchta@ohio.edu
A ring species is a circular arrangement of populations with reproductively isolated parts overlapping at one location, but with morphological and genetic intergradation among all other adjacent populations. The polymorphic salamander Ensatina eschscholtzii is widely considered a premier example of a ring species. In particular, the Ensatina complex was proposed by R. C. Stebbins to have originated in northern California and then expanded south down the inland ranges and the coastal ranges, the distributional arms adapting and diverging as they spread, until they recontacted as reproductively isolated populations in southern California. In a series of phylogeographic studies, David Wake and associates tested the major tenets of this model and found that the biogeography of E. eschscholtzii was far more complex than originally postulated. In this talk I will review patterns of phenotypic and genetic variation and how they inform us about the biogeography of E. eschscholtzii. I will also review Wake’s perspective on how species form, both from his written work and my memories of our conversations. In doing so, I will address why Wake preferred the Ensatina complex remain a single polytypic species and why he grew to dislike the word “speciation.” |
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4. 10:45 Morphological Species Delimitation of the Cryptic Northern and Southern Pacific Pond Turtles (Actinemys marmorata, Actinemys pallida). Robert Burroughs*, Seattle Children's Research Institute; Kenneth Angielczyk, Field Museum; Bryan Stuart, North Carolina Museum of Natural Sciences; James Parham, California State University Fullerton; Peter Smits, Truveta Incorporated robert.w.burroughs@gmail.com
The Pacific pond turtle, Actinemys, is distributed broadly and solely within the California Floristic Province. This broad distribution has supported the investigation of biogeographic evolution in Actinemys. Early studies uncovered an apparent clinal pattern of variation that led to the erection of two species Actinemys marmorata and Actinemys pallida; based on the presence or absence of an inguinal scute. Subsequent studies recognized that the inguinal scute was variably present within both species. Additional studies utilized molecular techniques to determine if Actinemys should be divided into at least two species. Results of these studies were ambiguous, suggesting that there may be multiple cryptic species. We investigate if there are morphological distinctions of these proposed cryptic species using supervised machine learning methods (MLMs) to evaluate geometric morphometrics on the plastron. We sampled 776 Actinemys specimens from across the geographic range and attempted to classify individuals to a species based on published biogeographic hypotheses. We also considered shape variation due to inguinal scute presence/absence, sex, and climate variables. We found that presence/absence of inguinal scutes, sex, and climatic variables do not appear to play a significant role in shape variation within the plastron of Actinemys. Performance of MLMs ultimately support the biogeographic hypothesis that splits Actinemys into two species Actinemys marmorata and Actinemys pallida. These results provide morphological support for the previous recognized species split and provide a framework forward for future investigation within Actinemys and in other groups where cryptic speciation is of interest. |
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5. 11:00 Exploring phenotype divergence among incipient species: A case study from the Southern Alligator Lizard species complex (Elgaria multicarinata spp). Rory Telemeco*, California State University telemeco@mail.fresnostate.edu
The molecular revolution has provided immense power to identify cryptic species but how functionally similar these species are is frequently unclear. Assessing functional phenotypic differences is critical for understanding the evolution and ecology of incipient species, and for developing management strategies. The Southern Alligator Lizard (Elgaria multicarinata) is one such example where molecular evidence suggests that at least two cryptic species were historically lumped, despite being evolutionarily independent for at least 4 million years. I examined the physiology and morphology of the two major lineages within the E. multicarinata species complex (Northern and Southern clades) to assess their phenotypic and functional divergence. The clades did not differ physiologically in any life-history stage examined. Clade of origin neither affected how embryos responded to thermal variation during development, nor whole-organism performance of adults in response to the thermal or oxygen environment. Similarly, head morphology was nearly indistinguishable between the clades, although the Northern clade displayed detectable sexual head dimorphism whereas the Southern clade did not. This difference in dimorphism might suggest ecological niche partitioning between the sexes of the Northern clade, or could suggest variation in sexual selection between the clades, either of which might function as a reproductive isolating mechanism. Our data suggest that these cryptic alligator lizard species are functionally indistinguishable despite millions of years of independent evolution. |
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6. 11:15 Biogeography and Diversification of Western Fence Lizards at their Northern Extreme in the Pacific Northwest. Hayden R. Davis*, University of Washington; Simone Des Roches, University of Washington; Roger A. Anderson, Western Washington University; Adam D. Leaché, University of Washington hrdavis1@uw.edu
Population dynamics within species at the edge of their distributional range, including the formation of genetic structure during range expansion, are difficult to study when they have had limited time to evolve. Western Fence Lizards (Sceloporus occidentalis) have a patchy distribution at the northern edge of their range around the Puget Sound, Washington, where they almost exclusively occur on imperiled coastal habitats. The entire region was covered by Pleistocene glaciation as recently as 16,000 years ago, suggesting that populations must have colonized these habitats relatively recently. We tested for population differentiation across this landscape using genome-wide SNPs and morphological data. A time-calibrated species tree supports the hypothesis of a post-glacial establishment and subsequent population expansion into the region. Despite a strong signal for fine-scale population genetic structure across the Puget Sound with as many as 8 – 10 distinct subpopulations supported by the SNP data, there is minimal evidence for morphological differentiation at this same spatiotemporal scale. Historical demographic analyses suggest that populations expanded and diverged across the region as the Cordilleran Ice Sheet receded. Population isolation, lack of dispersal corridors, and strict habitat requirements are the key drivers of population divergence in this system. These same factors may prove detrimental to the future persistence of populations as they cope with increasing shoreline development associated with urbanization. |
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7. 11:30 Colonization history and lineage diversification for three lizard taxa inhabiting the California Channel Islands. Patricia Salerno, Universidad Tecnológica Indoamérica; Lauren Chan*, Pacific University; Gregory Pauly, Natural History Museum of Los Angeles County; W. Chris Funk, Colorado State University; Jeanne Robertson, California State University chan5416@pacificu.edu
Near-shore island systems host taxon assemblages that closely mirror mainland communities. In some cases, geographic isolation may be sufficient to reduce dispersal to islands accelerating lineage divergence from the mainland and the evolution of unique insular biota. The California Channel Islands are an archipelago of eight near-shore islands of relatively recent age that differ in size, topography, and distance to the mainland. Our aim is to elucidate the colonization histories and patterns of connectivity among Channel Island populations of three lizard species (western fence lizard, Sceloporus occidentalis; southern alligator lizard, Elgaria multicarinata; common side-blotched lizard, Uta stansburiana). We present phylogeographic analyses of mitochondrial DNA sequences from each of these three species covering their entire island distributions plus adjacent California mainland. We find unique histories of colonization and dispersal for each species which we interpret in light of microfossil evidence and historical and contemporary anthropogenic activity on the islands. We find support for the treatment of S. occidentalis as an endemic island species, S. becki. For E. multicarinata, our data provide support for long-standing populations on the islands, but with recent inter-island connectivity. For U. stansburiana, shallow genetic differentiation between the islands and mainland California supports at least two mainland-to-island colonization events. We provide taxon-specific conservation management recommendations for these island taxa. |