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Evolutionary biologists commonly seek explanations for how selection drives the emergence of novel traits. Although trait loss is also predicted to occur frequently, few contemporary examples exist. In Hawaii, the Pacific field cricket (Teleogryllus oceanicus) is undergoing adaptive sexual signal loss due to natural selection imposed by eavesdropping parasitoids. Mutant male crickets (“flatwings”)...
Speciation occurs when reproductive barriers substantially reduce gene flow between lineages. Understanding how specific barriers contribute to reproductive isolation offers insight into the initial forces driving divergence and the evolutionary and ecological processes responsible for maintaining diversity. Here, we quantified multiple pre‐ and post‐pollination isolating barriers in a pair of closely...
Species adapt to the selective pressures of novel environments. Here, Gleditsch and Sperry tested whether four nonnative frugivorous bird species on the Hawaiian island of O'ahu diverged morphologically from their ancestral populations. They found that all four species significantly diverged from populations in their native ranges, with a general trend of smaller body size and larger bills. These...
The causes and consequences of fluctuating population densities are an important topic in ecological literature. Yet, the effects of such fluctuations on maintenance of variation in spatially structured populations have received little analytic treatment. We analyze what happens when two habitats coupled by migration not only differ in their trade‐offs in selection but also in their demographic stability—and...
The generation of reproductive incompatibility between groups requires a rare genotype with low compatibility to increase in frequency. We tested the hypothesis that sexual conflict driven by the risk of polyspermy can generate compatibility groups in gamete recognition proteins (GRPs) in the sea urchin Mesocentrotus franciscanus. We examined variation in the sperm (bindin) and egg (EBR1) GRPs, how...
Host–parasite relationships are often cited as classic examples of coevolution, but parasites are also able to switch hosts. Is the distribution of parasites across a phylogeny affected by the phylogenetic distance between potential hosts? Engelstädter and Fortuna (2019) provide evidence that the success of host switches is linked to phylogenetic distance between potential hosts, as well as the diversification...
Mediterranean‐type ecosystems (MTEs) contain exceptional plant diversity. Explanations for this diversity are usually classed as either “equilibrium,” with elevated MTE diversity resulting from greater ecological carrying capacities, or “non‐equilibrium,” with MTEs having a greater accumulation of diversity over time than other types of ecosystems. These models have typically been considered as mutually...
Endosymbionts sometimes help their hosts resist parasites, but does infection of pea aphids (Acyrthosiphon pisum) with different strains of the endosymbiont Spiroplasma confer fitness benefits that offset the costs? Mathé‐Hubert et al. found that across four life‐history traits, Spiroplasma infection induced negative effects on host fitness when compared to controls. Only two of 12 strains of Spiroplasma...
Natural infections often consist of multiple pathogens of the same or different species. When coinfections occur, pathogens compete for access to host resources and fitness is determined by how well a pathogen can reproduce compared to its competitors. Yet not all hosts provide the same resource pool. Males and females, in particular, commonly vary in both their acquisition of resources and investment...
Parasites often jump to and become established in a new host species. There is much evidence that the probability of such host shifts decreases with increasing phylogenetic distance between donor and recipient hosts, but the consequences of such preferential host switching remain little explored. We develop a computational model to investigate the dynamics of parasite host shifts in the presence of...
Existing radiations in a spatially limited system such as an oceanic island may limit the ecological opportunity experienced by later colonists, resulting in lower macroevolutionary rates for secondary radiations. Additionally, potential colonists may be competitively excluded by these incumbent (resident) species, unless they are biologically distinct (biotic filtering). The extant phenotypic diversity...
Novel ecosystems have become widespread created, in part, by the global spread of species. The nonnative species in these environments can be under intense evolutionary pressures that cause rapid morphological change, which can then influence species interactions. In Hawaii, much of the native frugivore community is extinct, replaced by nonnative bird species. Here, we determined if the passerine...
Do primary radiations inhibit the persistence and diversification of secondary colonizers? Rowsey et al. test predictions of this “incumbency effect” by contrasting patterns of morphological variation in two murine rodent clades on the Philippine island of Luzon. They find that in this system, primary colonizers may impose constraints via biotic filtering, and may also restrict size evolution in secondary...
The heritable endosymbiont Spiroplasma infects many insects and has repeatedly evolved the ability to protect its hosts against different parasites. Defenses do not come for free to the host, and theory predicts that more costly symbionts need to provide stronger benefits to persist in host populations. We investigated the costs and benefits of Spiroplasma infections in pea aphids (Acyrthosiphon pisum...
The environment changes constantly at various time scales and, in order to survive, species need to keep adapting. Whether these species succeed in avoiding extinction is a major evolutionary question. Using a multilocus evolutionary model of a mutation‐limited population adapting under strong selection, we investigate the effects of the frequency of environmental fluctuations on adaptation. Our results...
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