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Evolution in nature occurs in the proverbial tangled bank. The species interactions characterizing this tangled bank can be strongly affected by global change and can also influence the fitness and selective effects of a global change on a focal population. As a result, species interactions can influence which traits will promote adaptation and the magnitude or direction of evolutionary responses to the global change. First, we provide a framework describing how species interactions may influence evolutionary responses to global change. Then, we highlight case studies that have explicitly manipulated both a global change and the presence or abundance of interacting species and used either experimental evolution or quantitative genetics approaches to test for the effects of species interactions on evolutionary responses to global change. Although still not frequently considered, we argue that species interactions commonly modulate the effects of global change on the evolution of plant and animal populations. As a result, predicting the evolutionary effects of the multitude of global changes facing natural populations requires both community ecology and evolutionary perspectives.

 

Symbionts within the familySymbiodiniaceaeare important on coral reefs because they provide significant amounts of carbon to many different reef species. The breakdown of this mutualism that occurs as a result of increasingly warmer ocean temperatures is a major threat to coral reef ecosystems globally. Recombination during sexual reproduction and high rates of somatic mutation can lead to increased genetic variation within symbiont species, which may provide the fuel for natural selection and adaptation. However, few studies have asked whether such variation in functional traits exists within these symbionts. We used several genotypes of two closely related species,Breviolum antillogorgiumandB. minutum, to examine variation of traits related to symbiosis in response to increases in temperature or nitrogen availability in laboratory cultures. We found significant genetic variation within and among symbiont species in chlorophyll content, photosynthetic efficiency, and growth rate. Two genotypes showed decreases in traits in response to increased temperatures predicted by climate change, but one genotype responded positively. Similarly, some genotypes within a species responded positively to high‐nitrogen environments, such as those expected within hosts or eutrophication associated with global change, while other genotypes in the same species responded negatively, suggesting context‐dependency in the strength of mutualism. Such variation in traits implies that there is potential for natural selection on symbionts in response to temperature and nutrients, which could confer an adaptive advantage to the holobiont.

 

Abstract Coral reef ecosystems are under threat from the frequent and severe impacts of anthropogenic climate change, particularly rising sea surface temperatures. The effects of thermal stress may be ameliorated by adaptation and/or acclimation of the host, symbiont, or holobiont (host + symbiont) to increased temperatures. We examined the role of the symbiont in promoting thermal tolerance of the holobiont, using Antillogorgia bipinnata (octocoral host) and Breviolum antillogorgium (symbiont) as a model system. We identified five distinct genotypes of B. antillogorgium from symbiont populations isolated from Antillogorgia colonies in the Florida Keys. Three symbiont genotypes were cultured and maintained at 26 °C (ambient historical temperature), and two were cultured and maintained at 30 °C (elevated historical temperature) for 2 yrs. We analyzed the growth rate and carrying capacity of each symbiont genotype at both ambient and elevated temperatures in culture (in vitro). All genotypes grew well at both temperatures, indicating that thermal tolerance exists among these B. antillogorgium cultures. However, a history of long-term growth at 30 °C did not yield better performance for B. antillogorgium at 30 °C (as compared to 26 °C), suggesting that prior culturing at the elevated temperature did not result in increased thermal tolerance. We then inoculated juvenile A. bipinnata polyps with each of the five symbiont genotypes and reared these polyps at both ambient and elevated temperatures ( in hospite experiment). All genotypes established symbioses with polyps in both temperature treatments. Survivorship of polyps at 30 °C was significantly lower than survivorship at 26 °C, but all treatments had surviving polyps at 56 d post-infection. Our results suggest broad thermal tolerance in B. antillogorgium, which may play a part in the increased resilience of Caribbean octocorals during heat stress events. 

Abstract Two isolated clades of the lined shore crab, Pachygrapsus crassipes , live on opposite sides of the northern Pacific, presenting an interesting opportunity for studies of range limits and divergence. Prior to this study, P. crassipes ’ Asian range was unclear; we confirmed that it is found throughout the main Japanese Archipelago, though sporadic or absent from the Ryukyu Archipelago. We examined phenotypic variation of this species’ chelae, which are conspicuously colored and larger in males, and found positive allometry for both sexes, which was stronger in males, a common feature of sexually selected ornaments and weapons. We also found that Asian and North American clades differ significantly in chela reflectance — in contrast to previous studies, which stated that these clades were phenotypically identical. We conclude that these clades are diverging phenotypically, but that these differences are not yet sufficient to warrant distinction as separate species. 

Lemur catta is the most reported illegal captive lemur. We document 286 L. catta that were held in illegal captive conditions in Madagascar. Coastal tourist destinations are “hot spots” for sightings. Many of the L. catta reported were in businesses (49%) and were perceived to be held captive for the purpose of generating income (41%). Infant/juvenile L. catta were overwhelmingly observed annually in December (41%) and may suffer high mortality rates given that they are not weaned during this month of the year. Population growth modeling suggests that known capture rates may be sustainable in all but small populations of 500 individuals and when infants/juveniles are targeted. However, of the seven remaining populations of L. catta with more than 100 individuals, only one is known to contain more than 500 animals, and we present evidence here that infants/juveniles are targeted. Moreover L. catta face significant other threats including habitat loss, bushmeat hunting, and climate change. Several actions could reduce the illegal capture and ownership of L. catta in Madagascar such as tourist behavior change initiatives, enforcement of laws, and alternative livelihoods for local people. These interventions are urgently needed and could be adapted to protect other exploited wildlife in the future.