Population Structure and Conservation Genetics of the Oregon Spotted Frog, Rana Pretiosa

The Oregon spotted frog (Rana pretiosa) is one of the most threatened amphibians in the Pacific Northwest. Here we analyzed data from 13 microsatellite loci and 298 bp of mitochondrial DNA in frogs collected from 23 of the remaining R. pretiosa populations in order to (1) assess levels of genetic diversity within populations of R. pretiosa, (2) identify the major genetic groups in the species, (3) estimate levels of genetic differentiation and gene flow among populations within each major group, and (4) compare the pattern of differentiation among R. pretiosa populations with that among populations of R. cascadae, a non-endangered congener that also occurs in Oregon and Washington. There is a strong, hierarchical genetic structure in R. pretiosa. That structure includes six major genetic groups, one of which is represented by a single remaining population. R. pretiosa populations have low genetic diversity (average He = 0.31) compared to R. cascadae (average He = 0.54) and to other ranid frogs. Genetic subdivision among populations is much higher in R. pretiosa than in R. cascadae, particularly over the largest geographic distances (hundreds of kilometers). A joint analysis of migration rates among populations and of effective sizes within populations (using MIGRATE) suggests that both species have extremely low migration rates, and that R. pretiosa have slightly smaller effective sizes. However, the slight difference in effective sizes between species appears insufficient to explain the large difference in genetic diversity and in large-scale genetic structure. We therefore hypothesize that low connectivity among the more widely-spaced R. pretiosa populations (owing to their patchier habitat), is the main cause of their lower genetic diversity and higher among-population differentiation. Conservation recommendations for R. pretiosa include maintaining habitat connectivity to facilitate gene flow among populations that are still potentially connected, and either expanding habitat or founding additional \u27backup\u27 populations to maintain diversity in the isolated populations. We recommend that special consideration be given to conservation of the Camas Prairie population in Northern Oregon. It is the most geographically isolated population, has the lowest genetic diversity (He = 0.14) and appears to be the only remaining representative of a major genetic group that is now almost extinct. Finally, because the six major groups within R. pretiosa are strongly differentiated, occupy different habitat types, and are geographically separate, they should be recognized as evolutionarily significant units for purposes of conservation planning

Population and conservation genetic structure of the Cascades frog, Rana cascadae throughout the species' range

A major goal of conservation biology is to elucidate the population genetic structure in threatened species and assess the relative importance of the evolutionary forces that shape that population genetic structure. I conducted three studies in the declining amphibian Rana cascadae to assess levels of population genetic differentiation and the relative importance of gene flow versus random genetic drift throughout the species' range. In the first study, 1 examined phylogeographic structure on a species-wide geographic scale with both mitochondrial and nuclear molecular markers. I found three mitochondrial groups within R. cascadae that are as divergent at the mitochondrial DNA as sister species. However, I only found two nuclear groups within R. cascadae, suggesting there are two Distinct Population Segments and three Management Units within the species' range. In the second study, I compared sequence data from mtDNA and nuclear DNA of the three R. cascadae mtl)NA groups to several closely related Pacific Northwestern ranid species. I found the surprising result that the mtDNA of R. aurora aurora is more closely related to the mtDNA of' R. cascadae than to the mtDNA of its own subspecies R. aurora drayloni. The nuclear data support the sub-specific relationship between R. aurora aurora and R. aurora draytoni. This result is most likely due to incomplete lineage sorting of ancestral mtDNA alleles. Finally, in the third study, I examined the relative importance of gene flow versus random genetic drift on a fine geographic scale using microsatellite loci. Additionally, I estimated the long-term effective population sizes and genetic neighborhood size for 11 R. cascadae populations. Rana cascadae shows extreme isolation by distance with very little gene flow occurring past a distance of 10 km. Long-term effective population sizes were unrealistically large for current effective population sizes, but the estimates oF genetic neighborhood size are consistent with those expected based on current census population size and genetic neighborhood size in other amphibians. My research suggests Rana cascadae should be managed as three separate groups corresponding to the Olympic Peninsula, the Cascades of Washington and Oregon, and Northern California. Additionally, R. cascadae exhibits extreme isolation by distance with reduced gene flow at distances greater than 10 km, suggesting metapopulation structure is weak, and populations that go extinct are unlikely to be re-colonized quickly despite the presence of nearby R. cascadae populations

The Effects of Heterospecific Mating Frequency on the Strength of Cryptic Reproductive Barriers

Heterospecific mating frequency is critical to hybrid zone dynamics and can directly impact the strength of reproductive barriers and patterns of introgression. The effectiveness of post-mating prezygotic (PMPZ) reproductive barriers, which include reduced fecundity via heterospecific matings and conspecific sperm precedence, may depend on the number, identity and order of mates. Studies of PMPZ barriers suggest that they may be important in many systems, but whether these barriers are effective at realistic heterospecific mating frequencies has not been tested. Here, we evaluate the strength of cryptic reproductive isolation in two leaf beetles (Chrysochus auratus and C. cobaltinus) in the context of a range of heterospecific mating frequencies observed in natural populations. We found both species benefited from multiple matings, but the benefits were greater in C. cobaltinus and extended to heterospecific matings. We found that PMPZ barriers greatly limited hybrid production by C. auratus females with moderate heterospecific mating frequencies, but that their effectiveness diminished at higher heterospecific mating frequencies. In contrast, there was no evidence for PMPZ barriers in C. cobaltinus females at any heterospecific mating frequency. We show that integrating realistic estimates of cryptic isolation with information on relative abundance and heterospecific mating frequency in the field substantially improves our understanding of the strong directional bias in F1 production previously documented in the Chrysochus hybrid zone. Our results demonstrate that heterospecific mating frequency is critical to understanding the impact of cryptic post-copulatory barriers on hybrid zone structure and dynamics, and that future studies of such barriers should incorporate field-relevant heterospecific mating frequencies

Extreme Isolation By Distance in a Montane Frog Rana Cascadae

Given the recent interest in declining amphibian populations, it is surprising that there are so few data on genetic drift and gene flow in anuran species. We used seven microsatellite loci to investigate genetic structure and diversity at both large and small geographic scales, and to estimate gene flow in the Cascades frog, Rana cascadae. We sampled 18 sites in a hierarchical design (inter-population distances ranging from 1-670 km) to test for isolation by distance and to determine the geographic scale over which substantial gene flow occurs. Eleven of these sites were sampled as three fine-scale clusters of three, three, and five sites separated by pairwise distances of 1-23 km to estimate number of migrants exchanged per generation via F ST and by a coalescent approach. We found R. cascadae exhibits a strong pattern of isolation by distance over the entire species range, and that there is a sharp drop in migrants exchanged between sites separated by greater than 10 km. These data, in conjunction with results of other recent studies, suggest that montane habitats promote unusually strong genetic isolation among frog populations. We discuss our results in light of future management and conservation of R. cascadae

Genetic Structure in a Montane Ranid Frog: Restricted Gene Flow and Nuclear-Mitochondrial Discordance

There is substantial debate over the criteria that should be used to group populations of a species into distinct units for conservation (e.g. evolutionarily significant units, management units, distinct population segments). However, in practice molecular genetic differentiation is often the only or main criterion used to identify such units. Most genetic studies attempting to define conservation units in animals use a single molecular marker, most often mitochondrial, and use samples from a limited number of populations throughout the species\u27 range. Although there are many benefits to using mtDNA, certain features can cause it to show patterns of differentiation among populations that do not reflect the history of differentiation at the nuclear genome where loci controlling traits of adaptive significance presumably occur. Here we illustrate an example of such mitochondrial-nuclear discordance in a ranid frog, and show how using mtDNA or nuclear loci alone could have led to very different conservation recommendations. We also found very high genetic differentiation among populations on a local scale, and discuss the conservation implications of our results

Extreme isolation by distance in a montane frog Rana cascadae. Conservation Genetics

Abstract Given the recent interest in declining amphibian populations, it is surprising that there are so few data on genetic drift and gene flow in anuran species. We used seven microsatellite loci to investigate genetic structure and diversity at both large and small geographic scales, and to estimate gene flow in the Cascades frog, Rana cascadae. We sampled 18 sites in a hierarchical design (inter-population distances ranging from 1-670 km) to test for isolation by distance and to determine the geographic scale over which substantial gene flow occurs. Eleven of these sites were sampled as three fine-scale clusters of three, three, and five sites separated by pairwise distances of 1-23 km to estimate number of migrants exchanged per generation via F ST and by a coalescent approach. We found R. cascadae exhibits a strong pattern of isolation by distance over the entire species range, and that there is a sharp drop in migrants exchanged between sites separated by greater than 10 km. These data, in conjunction with results of other recent studies, suggest that montane habitats promote unusually strong genetic isolation among frog populations. We discuss our results in light of future management and conservation of R. cascadae

Structure, Biodiversity, and Historical Biogeography of Nematode Faunas in Holarctic Ruminants: Morphological and Molecular Diagnoses for \u3ci\u3eTeladorsagia boreoarticus\u3c/i\u3e n. sp. (Nemadota: Ostertagiinae), Dimorphic Cryptic Species in Muskoxen (\u3ci\u3eOvibos moschatus\u3c/i\u3e)

Discovery of the ostertagiine nematode Teladorsagia boreoarcticus n. sp. in muskoxen, Ovibos moschatus, from the central Canadian Arctic highlights the paucity of knowledge about the genealogical and numerical diversity of nematode faunas characteristic of artiodactyls at high latitudes across the Holarctic. Teladorsagia boreoarcticus is a dimorphic cryptic species distinguished from Teladorsagia circumcincta/Teladorsagia trifurcata in domestic sheep by a 13% divergence in the ND4 region of mitochondrial DNA, constant differences in the synlophe, and significantly longer esophageal valve, spicules, gubernaculum, and bursa. Teladorsagia boreoarcticus represents an archaic component of the North American fauna and may have a Holarctic distribution in muskoxen and caribou. Recognition of T. boreoarcticus in muskoxen, in part, corroborates hypotheses for the existence of a cryptic species complex of Teladorsagia spp. among Caprinae and Cervidae at high latitudes and indicates the importance of climatological determinants during the late Tertiary and Pleistocene on diversification of the fauna. Also reinforced is the concept of the North American fauna as a mosaic of endemic and introduced species. Discovery of a previously unrecognized species of Teladorsagia has additional implications and clearly indicates that (1) our knowledge is incomplete relative to potentially pathogenic nematodes that could be exchanged among domestic and wild caprines; (2) we do not have sufficient knowledge of the fauna to understand the ecological control mechanisms (limitations) on dissemination and host range; and (3) an understanding of historical and geographical influences on the genealogical diversity and distribution of nematode faunas in domestic and wild ruminants is requisite to define the interface between agricultural and natural ecosystems across the Holarctic

First Occurence of the Invasive Hydrozoan Eucheilota maculata (Cnidaria: Hydrozoa) in New Jersey, USA

Eucheilota maculata (Hartlaub, 1894) is a small hydrozoan native to the Mediterranean and northeast Atlantic Ocean. Like many diminutive hydrozoans, their presence in new environments may go unnoticed due to their small size, limited medusae production, and morphological similarities with native species. We report on the first observation of this species in the western North Atlantic Ocean using 16S molecular sequence analysis and morphological evaluation. Additionally, medusae were collected using standardized zooplankton tows providing density estimates of their blooms. 232 individuals were present in our sampling efforts in 2019 and 2021. 65 individuals were collected in September 2019 from 4 different sites with density ranging from 0.19-11.7 individuals m-3. In 2021, the primary bloom occurred in July with densities exceeding 13 m-3 at one site, but their presence was also recorded in August and September, but at lower densities. Their increase in abundance may be related to the closure of the Oyster Creek Nuclear Generating Station in 2018, as none were observed during sampling in that year or the years prior in Barnegat Bay, New Jersey

Structure, Biodiversity, and Historical Biogeography of Nematode Faunas in Holarctic Ruminants: Morphological and Molecular Diagnoses for Teladorsagia Boreoarcticus N. Sp. (Nematoda: Ostertagiinae), a Dimorphic Cryptic Species in Muskoxen (Ovibos Moschatus)

Discovery of the ostertagiine nematode Teladorsagia boreoarcticus n. sp. in muskoxen, Ovibos moschatus, from the central Canadian Arctic highlights the paucity of knowledge about the genealogical and numerical diversity of nematode faunas characteristic of artiodactyls at high latitudes across the Holarctic. Teladorsagia boreoarcticus is a dimorphic cryptic species distinguished from Teladorsagia circumcincta/Teladorsagia trifurcata in domestic sheep by a 13% divergence in the ND4 region of mitochondrial DNA, constant differences in the synlophe, and significantly longer esophageal valve, spicules, gubernaculum, and bursa. Teladorsagia boreoarcticus represents an archaic component of the North American fauna and may have a Holarctic distribution in muskoxen and caribou. Recognition of T. boreoarcticus in muskoxen, in part, corroborates hypotheses for the existence of a cryptic species complex of Teladorsagia spp. among Caprinae and Cervidae at high latitudes and indicates the importance of climatological determinants during the late Tertiary and Pleistocene on diversification of the fauna. Also reinforced is the concept of the North American fauna as a mosaic of endemic and introduced species. Discovery of a previously unrecognized species of Teladorsagia has additional implications and clearly indicates that (1) our knowledge is incomplete relative to potentially pathogenic nematodes that could be exchanged among domestic and wild caprines; (2) we do not have sufficient knowledge of the fauna to understand the ecological control mechanisms (limitations) on dissemination and host range; and (3) an understanding of historical and geographical influences on the genealogical diversity and distribution of nematode faunas in domestic and wild ruminants is requisite to define the interface between agricultural and natural ecosystems across the Holarctic