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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Ecology and evolution of parent–embryo interactions in neotropical glassfrogs

Delia, Jesse 11 December 2018 (has links)
Parental care is important to offspring survival in many species. Because care benefits young and is often costly to parents, it can generate fitness trade-offs that influence the evolution of family life. In particular, interactions within families are predicted to generate variation in care, which in turn causes selection on traits used to give, receive, and influence care. My dissertation examines whether such socially dynamic processes have influenced the evolution of parental and embryo behavior in glassfrogs (Centrolenidae). These Neotropical frogs have terrestrial eggs, aquatic larvae, and multiple origins of male-only care. Embryos can plastically alter hatching age, which might allow them to adaptively respond to variation in egg care. I test for parent–embryo coevolution by combining field observations (40 species), experiments (8 species), and phylogenetic comparative analyses. First, I test historical and functional hypotheses of parental care evolution. I found that uniparental egg-care is ubiquitous in centrolenids, can be provided by either sex, and benefits young. Elaborate male-only care evolved repeatedly from simpler female-only care, a pattern consistent with constraints on female-care levels. Second, I examine the diversification of male-only care, testing whether maternal changes to egg-clutch traits influence embryo dependency and if such changes are associated with male-only care. Evidence indicates that reduced female expenditure on egg-jelly evolved with, and increases the importance of, elaborate male care. Next, I evaluate whether embryos respond to behavioral and evolutionary changes in parenting. Embryos behaviorally delay hatching when parents continue caring, and evidence indicates that evolutionary increases in hatching plasticity evolved with increases in care duration. I tested if male mating success causes variation in male care, and thereby influences embryo behavior. I found that increased mating success extends male care, making nests safer, and embryos delay hatching accordingly. Finally, I examine selective tradeoffs influencing hatching plasticity by measuring hatchling phenotypes and fitness correlates. Across species, delayed hatching provides performance benefits during the larval stage. Overall, my work reveals coevolutionary interactions among mothers, fathers, and embryos. It supports that embryos respond to parentally mediated changes in egg environments and elucidates how family life alters selection on parental and embryo traits.
2

Species Limits, and Evolutionary History of Glassfrogs

Castroviejo-Fisher, Santiago January 2009 (has links)
Recognizing the mechanisms of speciation and the limits of species is essential to understand the origin of biodiversity and how to conserve it. The general aims of my investigations during my doctoral studies were two-fold: to study evolutionary patterns and processes, and to provide specific and superspecific taxonomic classifications that try to reflect evolutionary history. I have focused my research on anurans in their biodiversity hotspot, the American Tropics. I have used morphological, behavioral (mating calls), and genetic (DNA sequences) characters to study species boundaries between frogs of the genus Pristimantis and the family Centrolenidae (glassfrogs). The results show that the exclusive use of single lines of evidence or the application of arbitrary thresholds impair and bias our ability to recognize new species and limit the possibility to understand evolutionary processes. Only an integrative approach combining every source of evidence provides the necessary feedback to discover all species and test their identity by comparing independent sets of data. This approach further allows identifying those species that probably represent stable comparative units (well supported species hypotheses) and to flag taxa that require further assessment. Phylogenetic reconstructions based on seven nuclear and mitochondrial genes for about 100 species of glassfrogs revealed that previous hypotheses of relationships were mislead by rampant convergent evolution at the phenotypic level. None of the previously suggested classifications fit with the reconstructed evolutionary history. Consequently, we proposed a new classification consistent with this phylogeny. I also studied the tempo and mode of diversification among glassfrogs. Based on sequences from ten genes in 87 species, I estimated species divergence times, age-range correlation between sister species, and reconstructed ancestral areas and dispersal/vicariance events. The results revealed a complex model of diversification where geographical isolation seems to be the dominant scenario for speciation and only clades of altitudinal generalists have been able to spread across the Neotropical rainforests.

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