Michael R. J. Forstner

Molecular systematics, phylogeography, and the effects of pleistocene glaciation in the painted turtle (Chrysemys picta) complex

Abstract.— The painted turtle, Chrysemys picta, is currently recognized as a continentally distributed polytypic species, ranging across North America from southern Canada to extreme northern Mexico. We analyzed variation in the rapidly evolving mitochondrial control region (CR) in 241 turtles from 117 localities across this range to examine whether the painted turtle represents a continentally distributed species based on molecular analysis. We found strong support for the novel hypothesis that C. p. dorsalis is the sister group to all remaining Chrysemys, with the remaining Chrysemys falling into a single, extremely wide‐ranging and genetically undifferentiated species. Given our goal of an evolu‐tionarily accurate taxonomy, we propose that two evolutionary lineages be recognized as species within Chrysemys: C. dorsalis (Agassiz 1857) in the southern Mississippi drainage region, and C. picta (Schneider 1783) from the rest of the range of the genus. Neither molecular nor recent morphological analyses argue for the hybrid origin of C. p. marginata as previously proposed. Within C. picta, we find evidence of at least two independent range expansions into previously glaciated regions of North America, one into New England and the other into the upper Midwest. We further find evidence of a massive extinction/recolonization event across the Great Plains/Rocky Mountain region encompassing over half the continental United States. The timing and extent of this colonization is consistent with a recently proposed regional aridification as the Laurentide ice sheets receded approximately 14,000 years ago, and we tentatively propose this paleoclimatological event as a major factor shaping genetic variation in Chrysemys.

The α-Actinin Gene Family: A Revised Classification

The sequencing of a genome is the first stage of its complete characterization. Subsequent work seeks to utilize available sequence data to gain a better understanding of the genes which are found within a genome. Gene families comprise large portions of the genomes of higher vertebrates, and the available genomic data allow for a reappraisal of gene family evolution. This reappraisal will clarify relatedness within and between gene families. One such family, the α-actinin gene family, is part of the spectrin superfamily. There are four known loci, which encode α-actinins 1, 2, 3, and 4. Of the eight domains in α-actinin, the actin-binding domain is the most highly conserved. Here we present evidence gained through phylogenetic analyses of the highly conserved actin-binding domain that α-actinin 2 was the first of the four α-actinins to arise by gene duplication, followed by the divergence of α-actinin 3 and then α-actinins 1 and 4. Resolution of the gene tree for this gene family has allowed us to reclassify several α-actinins which were previously given names inconsistent with the most widely accepted nomenclature for this gene family. This reclassification clarifies previous discrepancies in the public databases as well as in the literature, thus eliminating confusion caused by continued misclassification of members of the α-actinin gene family. In addition, the topology found for this gene family undermines the 2R hypothesis theory of two rounds of genome duplication early in vertebrate evolution.

A Reexamination of the Phylogenetic Position of Callimico (Primates) Incorporating New Mitochondrial DNA Sequence Data

Abstract. The New World monkeys are divided into two main groups, Callitrichidae and Cebidae. Callimico goeldii shares traits with both the Cebidae and the Callitrichidae. Recent morphological phyletic studies generally place Callimico as the most basal member of the Callitrichidae. In contrast, genetic studies (immunological, restriction fragment, and sequence data) have consistently placed Callimico somewhere within the Callitrichidae, not basal to this clade. A DNA sequence data set from the terminal 236 codons of the mitochondrial ND4 gene and the tRNAHis, tRNASer, and tRNALeu genes was generated to clarify the position of Callimico. The sequences of 887 base pairs were analyzed by maximum-parsimony, neighbor-joining, and maximum-likelihood methods. The results of these various methods are generally congruent and place Callimico within the Callitrichidae between the marmosets (Callithrix and Cebuella) and the tamarins (Saguinus and Leontopithecus). Combined analyses of all suitable nuclear and mitochondrial gene sequences confirm the position of Callimico between the marmosets and the tamarins. As available molecular evidence indicates that Callimico is more closely related to the marmosets than to the tamarins, a reconsideration of the morphological evidence in light of the consensus tree from DNA sequence analyses is warranted. The marmosets and tamarins share four morphological characters (loss of the third molar, loss of the hypocone, reduced body size, reproductive twinning). Dwarfism may have evolved repeatedly among the Callitrichidae. It is well-known that the loss of a character can occur many times independently. The reproduction of marmosets and tamarins is extremely specialized and it is difficult to imagine that this complex and unique twinning system evolved separately in marmosets and tamarins. However, it is possible that a secondary reversal to single offspring took place in Callimico.

Hybridization between Crocodylus acutus and Crocodylus moreletii in the Yucatan Peninsula: II. Evidence from microsatellites.

Detecting and quantifying hybridization between endangered or threatened taxa can provide valuable information with regards to conservation and management strategies. Hybridization between members of the genus Crocodylus has been known to occur in captivity and in some wild populations. We tested for hybridization among wild populations of American crocodile (C. acutus) and Morelets crocodile (C. moreletii) in the Yucatan Peninsula by comparing Bayesian assignment tests, based on microsatellite data, to mitochondrial and morphological assignments. Skin clips from 83 individuals were taken for genetic identification, and a total of 32 individuals (38.6%) exhibited some evidence of hybridization by combined morphological, mitochondrial and microsatellite analyses. The majority of hybrids were classified as F(2) hybrids and backcrosses to C. moreletii. Most of the introgression occurs in two national biosphere reserves located on the northern and eastern coasts of the Yucatan Peninsula. Preliminary tests did not find a significant decrease in hybridity across three life stages, thus far indicating a low level of selection against hybrids. Model-based analyses on multilocus genotypes of pure individuals returned little geographic partitioning in both C. acutus and C. moreletii.

Phylogenetic history of sifakas (Propithecus: Lemuriformes) derived from mtDNA sequences

The sifakas (Propithecus) include three species containing up to 10 described subspecies, whose evolutionary relationships remain contentious. In particular, it is unclear whether P. verreauxi deckeni and P.v. coronatus populations are differentiated at the subspecific level. Furthermore, the taxonomic status of the recently discovered P. tattersalli and its phylogenetic position also require further examination. About 2,400 bp of mitochondrial DNA sequence data from part of the COIII gene, together with complete genes for ND3, ND4L, ND4, and five tRNAs, were used to clarify relationships among Propithecus species and subspecies. All analyses group Avahi as the sister group to all sifakas. P. diadema is placed as a sister group to all other Propithecus. Among the remaining sifakas, one subclade is formed by P.v. coquereli and P. tattersalli, while P.v. verreauxi, P.v. deckeni, and P.v. coronatus form the second subclade. All analyses fail to resolve P.v. coronatus and P.v. deckeni into separate monophyletic lineages. Based on pairwise distance comparisons and tree topology, we conclude that P. tattersalli does not represent a distinct species and that P.v. deckeni and P.v. coronatus do not deserve subspecific rank. On the other hand, our analyses indicate that P.v. coquereli may well represent a separate species. Am. J. Primatol. 53:1–17, 2001.

Genetic characterization of captive Cuban crocodiles (Crocodylus rhombifer) and evidence of hybridization with the American crocodile (Crocodylus acutus).

There is a surprising lack of genetic data for the Cuban crocodile (Crocodylus rhombifer), especially given its status as a critically endangered species. Samples from captive individuals were used to genetically characterize this species in comparison with other New World crocodilians. Partial mitochondrial sequence data were generated from cyt-b (843 bp) and the tRNA(Pro)- tRNA(Phe)-D-loop region (442 bp). Phylogenetic analyses were performed by generating maximum parsimony, maximum likelihood, and Bayesian-based topologies. In addition, in an effort to identify species-specific alleles, ten polymorphic microsatellite loci were genotyped. Distance and model-based clustering analyses were performed on microsatellite data, in addition to a model-based assignment of hybrid types. Both mitochondrial and nuclear markers identified two distinct C. rhombifer genetic sub-clades (alpha and beta); and microsatellite analyses revealed that most admixed individuals were F(2) hybrids between C. rhombifer-alpha and the American crocodile (C. acutus). All individuals in the C. rhombifer-beta group were morphologically identified as C. acutus and formed a distinct genetic assemblage. J. Exp. Zool. 309A:649-660, 2008. (c) 2008 Wiley-Liss, Inc.

Admixture Analysis of Florida Largemouth Bass and Northern Largemouth Bass using Microsatellite Loci

Abstract Microsatellite DNA variation was examined at 11 loci in five populations of Florida largemouth bass Micropterus salmoides floridanus (N = 175) and eight populations of northern largemouth bass M. s. salmoides (N = 249). Distinct allele frequencies with 33 private alleles between subspecies (threshold frequency, ≥0.05) and 19 private alleles among three geographic regions distinguished between Florida largemouth bass and northern largemouth bass as well as between northern largemouth bass from northern and southern latitudes in North America. Variation at microsatellite loci also provided sufficient resolution to discriminate among some populations within regions. Allele frequencies indicated that of 37 trophy bass (defined here as fish weighing 5.90 kg or more) donated to the Texas Parks and Wildlife Department (TPWD) between 2004 and 2005, all had more than 50% Florida largemouth bass influence with ancestry genetically similar to that of populations sampled in western Florida. Some fish (N = 24...

Predation and the maintenance of color polymorphism in a habitat specialist squamate.

Multiple studies have addressed the mechanisms maintaining polymorphism within a population. However, several examples exist where species inhabiting diverse habitats exhibit local population-specific polymorphism. Numerous explanations have been proposed for the maintenance of geographic variation in color patterns. For example, spatial variation in patterns of selection or limited gene flow can cause entire populations to become fixed for a single morph, resulting in separate populations of the same species exhibiting separate and distinct color morphs. The mottled rock rattlesnake (Crotalus lepidus lepidus) is a montane species that exhibits among-population color polymorphism that correlates with substrate color. Habitat substrate in the eastern part of its range is composed primarily of light colored limestone and snakes have light dorsal coloration, whereas in the western region the substrate is primarily dark and snakes exhibit dark dorsal coloration. We hypothesized that predation on high contrast color and blotched patterns maintain these distinct color morphs. To test this we performed a predation experiment in the wild by deploying model snakes at 12 sites evenly distributed within each of the two regions where the different morphs are found. We employed a 2×2 factorial design that included two color and two blotched treatments. Our results showed that models contrasting with substrate coloration suffered significantly more avian attacks relative to models mimicking substrates. Predation attempts on blotched models were similar in each substrate type. These results support the hypothesis that color pattern is maintained by selective predation.

Detection of salmonellae in different turtle species within a headwater spring ecosystem.

Sediments and water from the slough arm of Spring Lake, the headwaters of the San Marcos River, Texas, USA, as well as swabs from biofilms on carapaces and from the cloacae of 18 common musk turtles (Sternotherus odoratus), 21 red-eared sliders (Trachemys scripta elegans), nine Texas river cooters (Pseudemys texana), one snapping turtle (Chelydra serpentina serpentina), and three Guadalupe spiny soft-shell turtles (Apalone spinifera guadalupensis), caught at the same site, were analyzed for salmonellae by culture and molecular techniques. Although enrichment cultures from sediment and water samples were negative for salmonellae in polymerase chain reaction (PCR)–based analyses, this technique detected salmonellae in the enrichments from both carapaces and cloacae of 11 musk turtles (61%), eight red-eared sliders (38%), and the snapping turtle. Salmo-nellae could also be detected in the enrichments from the carapaces of two additional red-eared sliders and two Texas river cooters; the remaining samples were negative. Further characterization of isolates obtained from the enrichment cultures of seven selected individuals that represented all turtle species with salmonellae confirmed the presence of Salmonella enterica subspecies enterica, with serovars Rubislaw, Newport, Gaminara, and Thompson identified. These results demonstrate the presence of different strains of potentially human pathogenic salmonellae naturally occurring on several turtle species with different life histories even within supposedly pristine environments.

Inferring Absence of Houston Toads Given Imperfect Detection Probabilities

Abstract