Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.

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Although the spatial separation of sexual organs within a flower (herkogamy) has been interpreted as a mechanism that promotes efficient pollen transfer, there have been few attempts to relate variation in herkogamy to probabilities of pollen flow. Here, we used a heterostylous species with variation in reciprocal herkogamy to test this hypothesis. We measured legitimate and illegitimate pollen flow with fluorescent dyes in four selected populations of Oxalis alpina corresponding to the extremes of a previously reported evolutionary gradient from tristyly to distyly. After the breakdown of tristyly, the observed increment in reciprocal herkogamy between the long and short morphs was associated with a 30% increase in the proportion of dye received from compatible illegitimate pollinations. In all populations, the most likely effective pollen vectors were two Heterosarus bee species. Our results support the adaptive value of reciprocal herkogamy in promoting efficient pollen transfer in heterostylous species.

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The immunocompetence handicap hypothesis (ICHH) states that hormones enhance sexual trait expression but impair immunity.Previous tests of the ICHH have been hampered by experimental design problems. Here, we report on an experimental test of the ICHH that includes manipulations of both hormones and infections in males of the territorial damselfly, Hetaerina americana, with accurate survival measurements. We conducted a fully factorial experiment subjecting each individual to one of three topical treatments: methoprene (a juvenile hormone analog), acetone, or control, and one of three injection treatments: bacteria, PBS, or control. We measured survival of manipulated males in both the wild and in captivity. As predicted, survival was most heavily impaired in methoprene-bacteria males than in the other groups in the wild, and no survival differences emerged in captive animals. This result confirms that survival is one cost an animal pays for increased hormonal levels. This corroborates theoretical predictions of the ICHH. K E Y W O R D S :Infection, insect, juvenile hormone analog, mark-recapture, Odonata, survival, sexual selection, trade-off.

1. Urbanisation causes important losses in biodiversity and ecosystem of animals. To test whether these negative effects are preceded by unhealthy individuals in urban populations, we evaluated the effects of urbanisation on the abundance and physical condition of the dung beetle Dichotomius guaribensis, an endemic species of the Brazilian Atlantic Forest.2. We sampled beetles in nine forest fragments with different urbanisation degrees, embedded in the urban matrix of the city of João Pessoa. Besides testing the abundance in each fragment, we quantified four indicators of physical condition in males and females: body size, body mass, energetic condition, and mite load.3. Females tended to be larger, and to have less lipid mass and more mites than males. Urbanisation had no effect on beetle abundance, but it negatively affected body mass and lipid content in males, but not females, revealing different sensitivities for both sexes. Body size and mite load were not affected by urbanisation in males or females. Fragment size had no effect on beetle abundance and physical condition in both sexes, suggesting that urbanisation has a greater impact than fragment size on beetle individual condition.4. In this study, we show that individual deterioration precedes population declines in disturbed environments, and our study opens new insights into the proximate causes that leads to the loss of biodiversity and ecosystem services in urbanised regions.

Host specialization after host shifting is traditionally viewed as the pathway to speciation in parasitic plants. However, geographical and environmental changes can also influence parasite speciation, through hybridization processes. Here we investigated the impact of past climatic fluctuations, environment, and host shifts on the genetic structure and patterns of hybridization and gene flow between Psittacanthus calyculatus and P. schiedeanus, a Mesoamerican species complex. Using microsatellites (408 individuals), we document moderate genetic diversity but high genetic differentiation between widespread parental clusters, calyculatus in dry pine-oak forests and schiedeanus in cloud forests. Bayesian analyses identified a third cluster, with admixture between parental clusters in areas of xeric and tropical dry forests and high levels of migration rates following secondary contact. Coincidently host associations in these areas differ from those in areas of parental species, suggesting that past hybridization played a role in environmental and host shifts. Overall, the observed genetic and geographic patterns suggest that these Psittacanthus populations could have entered a distinct evolutionary pathway. The results provide evidence for highlights on the importance of the Pleistocene climate changes, habitat differences, and potential host shifts in the evolutionary history of Neotropical mistletoes.

Ecosystem services provided by insects are threatened by recent increasing global temperatures, particularly in the tropics, where insects live close to their thermal limits. Given that tolerance to high temperatures depends on individual metabolism and physiological stress response, it may also be sensitive to other stressors that are common in natural and human-modified environments, such as pollution and parasite pressure. The effects of multiple stressors could be synergistic and can be particularly relevant in insects that provide highly valuable ecosystem services, such as dung beetles in cattle pastures. Here we measured heat tolerance (critical thermal maximum, CTmax) in dung beetles exposed to ivermectin, a toxic parasiticide excreted in cattle dung, with known negative effects on coprophagous fauna, and in beetles exposed to an immune challenge. We also exposed a group of beetles to a combination of both ivermectin and immune challenge to test for potential synergistic effects of both stressors. Contrary to our predictions, CTmax did not change with ivermectin exposure, but increased in immune-challenged beetles. As found in other insects, CTmax was higher in larger beetles, highlighting the importance of body size on thermal tolerance in ectotherms. We discuss potential mechanisms responsible of increased heat tolerance in immune-challenged beetles and highlight the importance of natural and human-induced environmental pressures that now interact with global warming and threaten ecosystem services provided by wild animals.