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Parental effects are often considered an evolved response, in which parents transmit information about the environment to enhance offspring fitness. However, these effects need not be adaptive. Here, we provide a striking example by presenting evidence that overfeeding of adult Mexican spadefoot toads, Spea multiplicata, is associated with decreased offspring survival. After a temporary change to their standard feeding regimen, S. multiplicata in our captive colony developed a much higher body condition (i.e. body mass for a given body length) than those in the wild. We analysed data from three subsequent experiments and found that although the body condition of a father was positively correlated with tadpole survival, mothers with a higher condition had lower tadpole survival. Our study highlights how obesity can negatively impact future generations via maladaptive maternal effects. Such effects could be especially likely for animals living in variable environments (such as spadefoots) that have evolved ‘thrifty phenotypes’ that make them prone to obesity. Our study also illustrates how husbandry conditions typically regarded as beneficial might be harmful. Given that captive breeding programmes are increasingly used to combat worldwide amphibian declines, these programmes must consider the ecology and evolutionary history of the focal species to minimize any maladaptive parental effects. 

Abstract Parental effects are often considered an evolved response, in which parents transmit information about the environment to enhance offspring fitness. However, these effects need not be adaptive. Here, we provide a striking example by presenting evidence that overfeeding of adult Mexican spadefoot toads, Spea multiplicata, is associated with decreased offspring survival. After a temporary change to their standard feeding regimen, S. multiplicata in our captive colony developed a much higher body condition (i.e. body mass for a given body length) than those in the wild. We analysed data from three subsequent experiments and found that although the body condition of a father was positively correlated with tadpole survival, mothers with a higher condition had lower tadpole survival. Our study highlights how obesity can negatively impact future generations via maladaptive maternal effects. Such effects could be especially likely for animals living in variable environments (such as spadefoots) that have evolved ‘thrifty phenotypes’ that make them prone to obesity. Our study also illustrates how husbandry conditions typically regarded as beneficial might be harmful. Given that captive breeding programmes are increasingly used to combat worldwide amphibian declines, these programmes must consider the ecology and evolutionary history of the focal species to minimize any maladaptive parental effects. 

Mating with another species is often maladaptive because it generally results in no or low-fitness offspring. When hybridization is sufficiently costly, individuals should avoid mating with heterospecifics even if it reduces their ability to mate with high-quality conspecifics that resemble heterospecifics. Here, we used spadefoot toads, Spea multiplicata, to evaluate whether females alter their preferences for conspecific male sexual signals (call rate) depending on heterospecific presence. When presented with conspecific signals against a background including both conspecific and heterospecific signals, females preferred male traits that were most dissimilar to heterospecifics—even though these signals are potentially associated with lower-quality mates. However, when these same females were presented with a background that included only conspecific signals, some females switched their preferences, choosing conspecific signals that were exaggerated and indicative of high-quality conspecific mates. Because only some females switched their preferences between these two chorus treatments, there was no population-level preference for exaggerated conspecific male signals in the absence of heterospecifics. These results show that hybridization risk can alter patterns of mate choice and, consequently, sexual selection on male signals. Moreover, they emphasize that the strength and expression of reproductive barriers between species (such as mate choice) can be context-dependent. 

Abstract Adaptive radiation plays a fundamental role in our understanding of the evolutionary process. However, the concept has provoked strong and differing opinions concerning its definition and nature among researchers studying a wide diversity of systems. Here, we take a broad view of what constitutes an adaptive radiation, and seek to find commonalities among disparate examples, ranging from plants to invertebrate and vertebrate animals, and remote islands to lakes and continents, to better understand processes shared across adaptive radiations. We surveyed many groups to evaluate factors considered important in a large variety of species radiations. In each of these studies, ecological opportunity of some form is identified as a prerequisite for adaptive radiation. However, evolvability, which can be enhanced by hybridization between distantly related species, may play a role in seeding entire radiations. Within radiations, the processes that lead to speciation depend largely on (1) whether the primary drivers of ecological shifts are (a) external to the membership of the radiation itself (mostly divergent or disruptive ecological selection) or (b) due to competition within the radiation membership (interactions among members) subsequent to reproductive isolation in similar environments, and (2) the extent and timing of admixture. These differences translate into different patterns of species accumulation and subsequent patterns of diversity across an adaptive radiation. Adaptive radiations occur in an extraordinary diversity of different ways, and continue to provide rich data for a better understanding of the diversification of life.