Abstract Temperature is one of the most important biological factors involved in ectotherm development, growth and reproduction. Temperature can have direct effects on phenotype, such as survival, development, or reproductive allocation. For example, parents may trade-off between producing fewer, larger eggs in cooler conditions, and more, smaller eggs in warm conditions. Additionally, temperature can also shape indirect (parental) effects in a process called transgenerational plasticity. However, the nature of temperature’s direct and indirect effects is poorly known in most species. In this study, we manipulated both parental and developmental thermal environment in a full-factorial, split-clutch design to investigate how thermal regime, both constant and diurnally fluctuating, impacts reproductive allocation and development of the freshwater snail Physa acuta, and if thermal regime has transgenerational effects. We found that temperature impacted life stages differently. Hot parental environments suppressed reproduction of parent snails, but hot developmental temperature accelerated development and growth of embryos compared with cooler developmental temperatures. We found no evidence that the thermal environment of parents affected any offspring trait, nor evidence of reproductive allocation strategies in response to temperature. These differential influences of ambient temperature on adult vs. juvenile life stages of P. acuta could have implications for population growth and survival under climate change.

Mating with close relatives ('inbreeding') is common in small, fragmented populations. Inbreeding leads to a higher frequency of loci with homozygous recessive alleles, which can have serious consequences for offspring fitness ('inbreeding depression'). In addition, females may differentially invest resources when they mate with a related or a nonrelated male, which might affect offspring fitness. A decline in the value of traits of inbred offspring, particularly traits displayed early in life, may therefore be caused by lower maternal investment when females mate with a relative (i.e. differential allocation) rather than solely being attributable to greater homozygosity of inbred offspring. In this study, we mated female guppies (Poecilia reticulata) to a brother or an unrelated male. We then measured the proportion of females breeding, their gestation time, offspring number, and offspring size at birth. We also tested if offspring traits are related to their mother's size, and their father's sexual coloration ('attractiveness'). Mating with a brother did not lower the gestation time, or the number or the size of offspring at birth. However, smaller females gave birth to fewer, smaller babies; and females mated to males with more black coloration gave birth significantly sooner. In addition, females were more likely to give birth when mated to a male with more black colouration, but only when he was an unrelated male, rather than their brother. In sum, reproductive success did not differ when a female mated with a brother or unrelated male. There was no evidence for either inbreeding depression or differential maternal allocation on early life history traits when mating with a relative.

Geographic variation in natural selection derived from biotic sources is an important driver of trait evolution. The evolution of Müllerian mimicry is governed by dual biotic forces of frequency-dependent predator selection and densities of prey populations consisting of conspecifics or congeners. Difficulties in quantifying these biotic forces can lead to difficulties in delimiting and studying phenomena such as mimicry evolution. We explore the spatial distribution of morphotypes and identify areas of high mimetic selection using a novel combination of methods to generate maps of mimetic phenotype prevalence in Ranitomeya poison frogs, a group of frogs characterized by great phenotypic variation and multiple putative Müllerian mimic pairs. We categorized representative populations of all species into four major recurring color patterns observed in Ranitomeya: striped, spotted, redhead, and banded morphs. We calculated rates of phenotypic evolution for each of the 4 morphs separately and generated ecological niche models (ENMs) for all species. We then split our species-level ENMs on the basis of intraspecific variation in color pattern categorization, and weighted ENM layers by relative evolutionary rate to produce mimicry maps. Our phenotypic evolutionary rate analyses identified multiple significant shifts in rates of evolution for the spotted, redhead, and banded phenotypes. Our mimicry maps successfully identify all suspected and known areas of Müllerian mimicry selection in Ranitomeya from the literature and show geographic areas with a gradient of suitability for Müllerian mimicry surrounding mimic hotspots. This approach offers an effective hypothesis generation method for studying traits that are tied to geography by explicitly connecting evolutionary patterns of traits to trends in their geographic distribution, particularly in situations where there are unknowns about drivers of trait evolution.