Sympatry between Two Wide-ranging Salamander Species

Understanding how closely related species coexist remains a central problem in community ecology. Habitat characteristics, presence of predators and competitors, and frequency of disturbance all affect the geographic distribution of a species. Plethodon cinereus and P. electromorphus are two closely related and ecologically similar species that have a large geographic overlap in their distributions. In this study, I had two main goals. First, I wanted to determine how commonly sympatric locations occurred between these two species. To address this goal, I conducted landscape-scale surveys in areas that should contain sympatric locations based on their distributions. My second goal was to determine if the relative number of individuals of each species within sympatric locations was stable over time by monitoring four sympatric locations over three years. In addition, flooding occurred during one year of the study, impacting two of the four monitored sympatric locations; therefore, I wanted to examine whether this disturbance affected the salamander populations at those locations. This flooding event provided a rare opportunity to study the impact of flooding on terrestrial salamanders, a topic about which little is known. I found that sympatric locations occurred less frequently than expected by chance and that some sympatric sites seem to be relatively stable while at others, the relative population size of P. cinereus was increasing — and that this shift might be positively affected by flooding. While this study demonstrated that P. cinereus and P. electromorphus do not occur in sympatry as frequently as expected by chance, the cause for this result is unknown. The most likely factor is that the two species exhibit subtle habitat differences that have not yet been demonstrated. The interactions between P. cinereus and P. electromorphus are complex, and the patterns observed here could have been generated by any number of mechanisms. Further research on this system could clarify some of these remaining questions

Ecological processes responsible for species co-occurrence patterns in two species of Plethodon salamanders

The competitive interactions of closely-related and ecologically similar species have long been considered an important topic in evolutionary ecology. These species interactions can have considerable effects on community composition and species distributions. Furthermore, ecological, behavioral, and morphological traits of species can be influenced by interactions with competitors. Throughout Ohio, two closely related and ecologically similar salamander species, Plethodon cinereus and P. electromorphus, occur in similar habitats and can be found in sympatry. Interestingly, the contact zone of these two species is much broader than has been observed in other pairs of Plethodon species that competitively interact. However, when these distributions are viewed at a finer scale, the two species do not always co-occur.;I examined the interactions of P. cinereus and P. electromorphus through a variety of methods to better understand how the interactions between these two species lead to their distributions in Ohio. I found that in sympatry, both species were more aggressive towards individuals of the other species than when each was found in allopatry, indicating that the process of alpha-selection may have led to the evolution of enhanced aggressive behavior in sympatry. Within some sympatric areas, P. cinereus may be excluding P. electromorphus through these interference mechanisms. In addition, disturbance processes, such as flooding, may have sped up this process of competitive exclusion in areas where flooding occurred. These two species were using the same resources, both refuge sites and prey resources, which suggests that if these resources are limiting, they would compete for them. At different sympatric sites, morphology is evolving in different ways, such that these two species become more divergent at some sites, more similar at some sites, and do not seem to be changing at other sites. Furthermore, morphological differences are associated with differences in food use across all the sites that were examined.;The distribution and persistence patterns of sympatric localities between P. cinereus and P. electromorphus suggest that these species respond to community processes in complex ways. It appears that competitive interactions between these two species in sympatry can lead to the evolution of character displacement or competitive exclusion of one species (likely P. electromorphus). Additionally, at least one sympatric site appears to be stable where intense aggression may have resulted in interspecific territoriality. In this system, complex interactions of competition and disturbance are shaping the observed distribution patterns of these two species. While the results of my research have shed light on these species interactions, further studies could reveal the potential impacts that additional competitors or predators may have on these distributions

Sympatry between Two Wide-ranging Salamander Species

Understanding how closely related species coexist remains a central problem in community ecology. Habitat characteristics, presence of predators and competitors, and frequency of disturbance all affect the geographic distribution of a species. Plethodon cinereus and P. electromorphus are two closely related and ecologically similar species that have a large geographic overlap in their distributions. In this study, I had two main goals. First, I wanted to determine how commonly sympatric locations occurred between these two species. To address this goal, I conducted landscape-scale surveys in areas that should contain sympatric locations based on their distributions. My second goal was to determine if the relative number of individuals of each species within sympatric locations was stable over time by monitoring four sympatric locations over three years. In addition, flooding occurred during one year of the study, impacting two of the four monitored sympatric locations; therefore, I wanted to examine whether this disturbance affected the salamander populations at those locations. This flooding event provided a rare opportunity to study the impact of flooding on terrestrial salamanders, a topic about which little is known. I found that sympatric locations occurred less frequently than expected by chance and that some sympatric sites seem to be relatively stable while at others, the relative population size of P. cinereus was increasing — and that this shift might be positively affected by flooding. While this study demonstrated that P. cinereus and P. electromorphus do not occur in sympatry as frequently as expected by chance, the cause for this result is unknown. The most likely factor is that the two species exhibit subtle habitat differences that have not yet been demonstrated. The interactions between P. cinereus and P. electromorphus are complex, and the patterns observed here could have been generated by any number of mechanisms. Further research on this system could clarify some of these remaining questions

Notes on Reproduction in the Brownback Salamander (Eurycea aquatica)

Life history data often are lacking for species with an uncertain taxonomic status. As phylogenetic analyses improve and our understanding of species boundaries become more refined, ecological information should likewise keep pace. Here, we report information on the timing of reproduction, clutch size, and nest attendance for the Brownback Salamander (Eurycea aquatica), a species recently documented to be a separate lineage after a long, controversial systematic history. We confirm that this species has the largest clutch size of any lineage within the Eurycea bislineata complex, and suggest that male and male-female nest attendance is not uncommon in this species. We suggest that, in addition to the genetic divergence documented between E. aquatica and other members of the E. bislineata complex, ecological differences also are present and possibly are influenced by the unique springs inhabited by Brownback Salamanders

Notes on Reproduction in the Brownback Salamander (Eurycea aquatica)

Life history data often are lacking for species with an uncertain taxonomic status. As phylogenetic analyses improve and our understanding of species boundaries become more refined, ecological information should likewise keep pace. Here, we report information on the timing of reproduction, clutch size, and nest attendance for the Brownback Salamander (Eurycea aquatica), a species recently documented to be a separate lineage after a long, controversial systematic history. We confirm that this species has the largest clutch size of any lineage within the Eurycea bislineata complex, and suggest that male and male-female nest attendance is not uncommon in this species. We suggest that, in addition to the genetic divergence documented between E. aquatica and other members of the E. bislineata complex, ecological differences also are present and possibly are influenced by the unique springs inhabited by Brownback Salamanders

Role of dispersal in resistance evolution and spread

Gene flow via immigration affects rate of evolution of resistance to a pest management tactic, while emigration from a resistant population can spread resistance alleles spatially. Whether resistance detected across the landscape reflects ongoing de novo evolution in different hotspots or spread from a single focal population can determine the most effective mitigation strategy. Pest dispersal dynamics determine the spatio-temporal scale at which mitigation tactics must be applied to contain or reverse resistance in an area. Independent evolution of resistance in different populations appears common but not universal. Conversely, spatial spread appears to be almost inevitable. However, rate and scale of spread depends largely on dispersal dynamics and interplay with factors such as fitness costs, spatially variable selection pressure and whether resistance alleles are spreading through an established population or being carried by populations colonizing new territory

What are the consequences of combining nuclear and mitochondrial data for phylogenetic analysis? Lessons from Plethodon salamanders and 13 other vertebrate clades

<p>Abstract</p> <p>Background</p> <p>The use of mitochondrial DNA data in phylogenetics is controversial, yet studies that combine mitochondrial and nuclear DNA data (mtDNA and nucDNA) to estimate phylogeny are common, especially in vertebrates. Surprisingly, the consequences of combining these data types are largely unexplored, and many fundamental questions remain unaddressed in the literature. For example, how much do trees from mtDNA and nucDNA differ? How are topological conflicts between these data types typically resolved in the combined-data tree? What determines whether a node will be resolved in favor of mtDNA or nucDNA, and are there any generalities that can be made regarding resolution of mtDNA-nucDNA conflicts in combined-data trees? Here, we address these and related questions using new and published nucDNA and mtDNA data for <it>Plethodon </it>salamanders and published data from 13 other vertebrate clades (including fish, frogs, lizards, birds, turtles, and mammals).</p> <p>Results</p> <p>We find widespread discordance between trees from mtDNA and nucDNA (30-70% of nodes disagree per clade), but this discordance is typically not strongly supported. Despite often having larger numbers of variable characters, mtDNA data do not typically dominate combined-data analyses, and combined-data trees often share more nodes with trees from nucDNA alone. There is no relationship between the proportion of nodes shared between combined-data and mtDNA trees and relative numbers of variable characters or levels of homoplasy in the mtDNA and nucDNA data sets. Congruence between trees from mtDNA and nucDNA is higher on branches that are longer and deeper in the combined-data tree, but whether a conflicting node will be resolved in favor mtDNA or nucDNA is unrelated to branch length. Conflicts that are resolved in favor of nucDNA tend to occur at deeper nodes in the combined-data tree. In contrast to these overall trends, we find that <it>Plethodon </it>have an unusually large number of strongly supported conflicts between data types, which are generally resolved in favor of mtDNA in the combined-data tree (despite the large number of nuclear loci sampled).</p> <p>Conclusions</p> <p>Overall, our results from 14 vertebrate clades show that combined-data analyses are not necessarily dominated by the more variable mtDNA data sets. However, given cases like <it>Plethodon</it>, there is also the need for routine checking of incongruence between mtDNA and nucDNA data and its impacts on combined-data analyses.</p

Weather and Populations of Small Mammals: A Twenty Year Study

This study investigated the relation between weather and population dynamics of small mammals. Prior studies have shown that changes in weather can alter population size by affecting mortality and fecundity rates. A twenty-year data set was used to detect correlations between weather factors and year-to-year fluctuations in population sizes of Feromyscus leucopus and Microtus pennsylvanicus. During the study (1977 to 1997), the field site underwent succession from a grassland to a forest. Annual population size was estimated using a mark-recapture trapping method in the fall of each year. Interannual variation in population size was analyzed using winter temperature, winter snowfall amount, summer temperature, and summer rainfall amount as independent variables. The analysis of weather effects also accounted for long-term habitat change. The implications of these results for the understanding of population fluctuations of small mammals are discussed

Ecological processes responsible for species co-occurrence patterns in two species of Plethodon salamanders

The competitive interactions of closely-related and ecologically similar species have long been considered an important topic in evolutionary ecology. These species interactions can have considerable effects on community composition and species distributions. Furthermore, ecological, behavioral, and morphological traits of species can be influenced by interactions with competitors. Throughout Ohio, two closely related and ecologically similar salamander species, Plethodon cinereus and P. electromorphus, occur in similar habitats and can be found in sympatry. Interestingly, the contact zone of these two species is much broader than has been observed in other pairs of Plethodon species that competitively interact. However, when these distributions are viewed at a finer scale, the two species do not always co-occur.;I examined the interactions of P. cinereus and P. electromorphus through a variety of methods to better understand how the interactions between these two species lead to their distributions in Ohio. I found that in sympatry, both species were more aggressive towards individuals of the other species than when each was found in allopatry, indicating that the process of alpha-selection may have led to the evolution of enhanced aggressive behavior in sympatry. Within some sympatric areas, P. cinereus may be excluding P. electromorphus through these interference mechanisms. In addition, disturbance processes, such as flooding, may have sped up this process of competitive exclusion in areas where flooding occurred. These two species were using the same resources, both refuge sites and prey resources, which suggests that if these resources are limiting, they would compete for them. At different sympatric sites, morphology is evolving in different ways, such that these two species become more divergent at some sites, more similar at some sites, and do not seem to be changing at other sites. Furthermore, morphological differences are associated with differences in food use across all the sites that were examined.;The distribution and persistence patterns of sympatric localities between P. cinereus and P. electromorphus suggest that these species respond to community processes in complex ways. It appears that competitive interactions between these two species in sympatry can lead to the evolution of character displacement or competitive exclusion of one species (likely P. electromorphus). Additionally, at least one sympatric site appears to be stable where intense aggression may have resulted in interspecific territoriality. In this system, complex interactions of competition and disturbance are shaping the observed distribution patterns of these two species. While the results of my research have shed light on these species interactions, further studies could reveal the potential impacts that additional competitors or predators may have on these distributions.</p

Effects of a Unique Source of Resistance in Soybeans and Seed Treatments on Soybean Cyst Nematode, Heterodera glycines, Reproduction and Soybean Yield in Minnesota

Soybean cyst nematode (Heterodera glycines Ichinohe; SCN) is one of the most devastating diseases of soybeans (Glycine max [L.] Merr.) in the United States. This disease is challenging to manage due to the lack of symptoms above ground and the lack of availability of soybean varieties with diverse SCN resistance genes that could be grown long term to slow development of SCN populations with increased reproduction. Soybean seed treatments have become an added tool for SCN management. For farmers to continue to grow soybean profitably in SCN-infested fields, SCN management needs to incorporate non-hosts crops, seed treatments, and soybean varieties developed with new resistance genetics. In this study, four field experiments were conducted in 2020 examining the effects of soybean varieties with different sources of resistance to SCN treated with different seed treatments on soybean yields and SCN population densities. The experiments were conducted in Mower (location 1), Dakota (location 2), Le Sueur (location 3), and Olmsted (location 4) Counties, Minnesota in fields that growers believed were infested with SCN. Yield data from one experiment was not used because of hail damage and another experiment had no detectable SCN population densities. There were no significant treatment effects on yield in the three experiments from which yield data were obtained. In the experiment at location 1, the SCN population densities at the end of season were significantly lower where soybeans with the Peking source of resistance were grown compared to soybeans with the PI88788 source of resistance and susceptible soybeans. Furthermore, SCN population densities for the variety with the PI89772 SCN source of resistance were similarly low and not significantly different from those with the Peking variety. In the experiment at location 2, the SCN population densities at the end of the season collected from soil sampling section 3 were significantly higher than soil sampling sections 1 and 2. There were no significant differences in SCN egg population densities among treatments for location 3, and SCN data from location 4 were not analyzed due to absence of SCN. Although this study did not detect significant treatment differences or interactions with respects to yield, the issue still stands that many growers are not aware of the impact SCN can have on their soybean yields and how there are ways in order to manage this disease, including adding seed treatments such as Saltro® and ILEVO® and planting SCN-resistant varieties with unique sources of SCN resistance, such as PI89772 and Peking.</p