The Evolution Of Placentas In Poeciliid Fishes

The history of biology is populated by numerous model species or organisms. But few vertebrate groups have aided evolutionary and ecological research more than the live-bearing fishes of the family Poeciliidae. Found throughout tropical and subtropical waters, poeciliids exhibit a fascinating variety of reproductive specializations, including viviparity, matrotrophy, unisexual reproduction, and alternative mating strategies, making them ideal models for research on patterns and processes in ecology, behavior, and evolution. Ecology and Evolution of Poeciliid Fishes is a much-needed overview of the scientific potential and understanding of these live-bearing fishes. Chapters by leading researchers take up a wide range of topics, including the evolution of unisexual reproduction, life in extreme environments, life-history evolution, and genetics. Designed to provide a single and highly approachable reference, Ecology and Evolution of Poeciliid Fishes will appeal to students and specialists interested in all aspects of evolutionary ecology.

Placental matrotrophy has evolved independently in many lineages, which is indicative of strong selection. Several ad-hoc hypotheses and one mathematical model have been proposed to explain its evolution, but little experimental data exists to support these claims. Recent studies have attempted to find correlates between placental matrotrophy and other life history traits, but the only common correlate found was a reduction in reproductive allocation (RA). Here I report on three studies. The first two focus on the Trexler-DeAngelis model for the evolution of matrotrophy. In chapter one, I use closely related placental and non-placental species from the northern clade of Poeciliopsis to test an assumption imperative to the model, that placental species abort a subset of developing offspring in low food conditions. The results show no evidence of abortion due to food level. Instead, placental species appear to be tethered to a brood once initiated, and sacrifice body condition to maintain reproduction when resources are restricted. However, an alternative explanation for these results is that the pattern of resource allocation is a function other life history traits, rather than placentation alone. Chapter two distinguishes between these alternatives, by performing a similar experiment on the southern clade of Poeciliopsis, which has the opposite relationship between life history traits and placentation seen in the northern clade. The results mirror those from the northern clade, indicating reproductive mode, rather than life history, dictates the pattern of resource allocation. This further adds to the difficulties of explaining the evolution of the placenta within the constraints of the Trexler-DeAngelis model. The third study characterizes locomotor consequences related to differences in reproductive allocation using the Trinidadian Guppy (Poecilia reticulata), because placentation is correlated with a reduction in reproductive allocation. Females with the highest RA were less streamlined, had lower escape velocities, and had to work harder during prolonged swimming. In low predation natural habitat, these same females were restricted to habitat with slower moving water, while females with lower RAs were able to use faster flows, which are thought to be preferred feeding grounds. All high predation fish used slow moving water, irrespective of RA.

The history of biology is populated by numerous model species or organisms. But few vertebrate groups have aided evolutionary and ecological research more than the live-bearing fishes of the family Poeciliidae. Found throughout tropical and subtropical waters, poeciliids exhibit a fascinating variety of reproductive specializations, including viviparity, matrotrophy, unisexual reproduction, and alternative mating strategies, making them ideal models for research on patterns and processes in ecology, behavior, and evolution. Ecology and Evolution of Poeciliid Fishes is a much-needed overview of the scientific potential and understanding of these live-bearing fishes. Chapters by leading researchers take up a wide range of topics, including the evolution of unisexual reproduction, life in extreme environments, life-history evolution, and genetics. Designed to provide a single and highly approachable reference, Ecology and Evolution of Poeciliid Fishes will appeal to students and specialists interested in all aspects of evolutionary ecology.

Of all vertebrates, fish exhibit unparalleled diversity of sexual plasticity and flexibility, ranging from gonochorism to unisexualism, and exceptional patterns of functional hermaphroditism. Fish farming and monosex aquaculture have led to reproductive dysfunction with males producing less milt, and females failing to ovulate and spawn. This book brings together relevant information on the role of the endocrine system on sexual differentiation in fish, and bridges the gap between molecular endocrinologists and fishery scientists.

The family-group names of animals (superfamily, family, subfamily, supertribe, tribe and subtribe) are regulated by the International Code of Zoological Nomenclature. Family names are particularly important because they are among the most widely used of all technical animal names. Apart from using the correct family-group name according to the Code, it is also important to use one unique universal name (with a fixed spelling) to avoid confusion. We have compiled a list of familygroup names for Recent fishes, applied the rules of the Code and, if possible, tried to conserve the names in prevailing recent practice. We list all of the family-group names found to date for Recent fishes (N=2625), together with their author(s) and year of publication. This list can be used in assigning the correct family-group name to a genus or a group of genera. With this publication we contribute to the usage of correct, universal family-group names in the classification of, and for communication about, Recent fishes.

An accessible modern guide to Darwin's masterwork Charles Darwin's Origin of Species is one of the most widely cited books in modern science. Yet tackling this classic can be daunting for students and general readers alike because of Darwin's Victorian prose and the complexity and scope of his ideas. The "Origin" Then and Now is a unique guide to Darwin's masterwork, making it accessible to a much wider audience by deconstructing and reorganizing the Origin in a way that allows for a clear explanation of its key concepts. The Origin is examined within the historical context in which it was written, and modern examples are used to reveal how this work remains a relevant and living document for today. In this eye-opening and accessible guide, David Reznick shows how many peculiarities of the Origin can be explained by the state of science in 1859, helping readers to grasp the true scope of Darwin's departure from the mainstream thinking of his day. He reconciles Darwin's concept of species with our current concept, which has advanced in important ways since Darwin first wrote the Origin, and he demonstrates why Darwin's theory unifies the biological sciences under a single conceptual framework much as Newton did for physics. Drawing liberally from the facsimile of the first edition of the Origin, Reznick enables readers to follow along as Darwin develops his ideas. The "Origin" Then and Now is an indispensable primer for anyone seeking to understand Darwin's Origin of Species and the ways it has shaped the modern study of evolution.