Premise
Evolution of cross‐pollination efficiency depends on the genetic variation of flower traits, the pollen vector, and flower trait matching between pollen donors and recipients. Trait matching ...has been almost unexplored among nonheterostylous species, and we examined whether the match of anther length in pollen donors and stigma length in pollen recipients influences the efficiency of cross‐pollination. To explore potential constraints for evolutionary response, we also quantified genetic variation and covariation among sepal length, petal length and width, stamen length, style length, and herkogamy.
Methods
We created 58 experimental arrays of Turnera velutina that varied in the extent of mismatch in the position of anthers and stigmas between single‐flowered plants. Genetic variation and correlations among flower traits were estimated under greenhouse conditions.
Results
Style length, but not herkogamy, influenced the efficiency of cross‐pollination. Plants with stamen length that matched the style length of other plants were more efficient pollen donors, whereas those with the style protruding above the stamens of other plants were more efficient pollen recipients. Significant broad‐sense heritability (0.22 > hB2 < 0.42) and moderate genetic correlations (0.33 > r < 0.85) among floral traits were detected.
Conclusions
Our results demonstrated that anther‐stigma mismatch between flowers contributed to variation in the efficiency of cross‐pollination. The genetic correlations between stamen length and other floral traits suggests that any change in cross‐pollination efficiency would be driven by changes in style rather than in stamen length.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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.
Urbanisation has negative effects on biodiversity that may be preceded by unhealthy individuals in urban populations.
Physical condition of dung beetles, but not their abundance, was negatively affected by increasing urbanisation.
By having individuals in low physical condition, cities may lose the function of ecosystem.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The evolution of sexual dimorphism in species with separate sexes is influenced by the resolution of sexual conflicts creating sex differences through genetic linkage or sex‐biased expression. Plants ...with different degrees of sexual dimorphism are thus ideal to study the genetic basis of sexual dimorphism. In this study we explore the genetic architecture of sexual dimorphism between Silene latifolia and Silene dioica. These species have chromosomal sex determination and differ in the extent of sexual dimorphism. To test whether QTL for sexually dimorphic traits have accumulated on the sex chromosomes and to quantify their contribution to species differences, we create a linkage map and performed QTL analysis of life history, flower and vegetative traits using an unidirectional interspecific F2 hybrid cross. We found support for an accumulation of QTL on the sex chromosomes and that sex differences explained a large proportion of the variance between species, suggesting that both natural and sexual selection contributed to species divergence. Sexually dimorphic traits that also differed between species displayed transgressive segregation. We observed a reversal in sexual dimorphism in the F2 population, where males tended to be larger than females, indicating that sexual dimorphism is constrained within populations but not in recombinant hybrids. This study contributes to the understanding of the genetic basis of sexual dimorphism and its evolution in Silene.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Pre‐ and post‐zygotic reproductive barriers are key components of reproductive isolation (RI) between taxa. Their timing of appearance and their strength can tell us about the underlying processes ...promoting differentiation between taxa in allopatry. Canthon cyanellus LeConte (Coleoptera: Scarabaeidae) represents a species complex that has diversified recently, and the species delimitation is still unclear. In this study, we performed experimental crosses to evaluate pre‐mating reproductive barriers between three subspecies of C. cyanellus: Canthon cyanellus cyanellus, Canthon cyanellus sallei, and Canthon cyanellus violetae. We further estimated post‐mating barriers by measuring fecundity and fertility in F1 and F2 generations in reciprocal crosses between two subspecies, C. c. cyanellus and C. c. sallei, and estimating the relative contribution of each barrier to total RI. Results showed that the subspecies are not strongly isolated overall, but asymmetric isolation was observed, with one cross accounting for 40% RI, whereas the other did not contribute to RI. Pre‐mating behavioral barriers accounted for a small fraction of total RI, whereas post‐mating (mostly post‐zygotic) barriers contributed to a larger extent. Fecundity and fertility in the F1 were higher than in parental populations, but this was strongly reduced in the F2. Our results suggest that diversification time between subspecies has been enough to accumulate genetic incompatibilities and indicate a faster accumulation of post‐ than pre‐zygotic reproductive barriers in this species complex.
Resumen
Las barreras reproductivas pre‐cigóticas y post‐cigóticas son componentes clave del aislamiento reproductivo (AR) entre taxones. El momento de aparición y su fuerza pueden informarnos sobre los procesos que promueven la diferenciación entre taxones en alopatría. Canthon cyanellus LeConte (Coleoptera: Scarabaeidae) representa un complejo de especies que se ha diversificado recientemente, y la delimitación de especies aún no está clara. En este estudio realizamos cruces experimentales para evaluar las barreras reproductivas pre‐apareamientos entre tres subespecies de Canthon cyanellus que han divergido recientemente. Además, estimamos las barreras posteriores al apareamiento midiendo la fecundidad y la fertilidad en las generaciones F1 y F2 en cruces recíprocos entre Canthon cynanellus cyanellus y Canthon cyanellus sallei y estimamos la contribución relativa de cada barrera al aislamiento reproductivo total. Los resultados mostraron que estas subespecies no están fuertemente aisladas en general (AR total = 18%), pero se encontró un aislamiento asimétrico con un cruce que explica el 40% del aislamiento reproductivo mientras que la otra no contribuyó. Las barreras pre‐apareamiento contribuyeron en menor medida al aislamiento, comparado con las barreras post‐apareamiento. La fecundidad y la fertilidad en la F1 fueron más altas que en las poblaciones parentales, pero fuertemente reducidas en la F2. Nuestros resultados sugieren que el tiempo de diversificación en este complejo de especies ha sido suficiente para acumular incompatibilidades genéticas, y una acumulación más rápida de barreras reproductivas post‐cigóticas que pre‐cigóticas.
In allopatric populations, various ecological pressures can promote the evolution of reproductive barriers. We evaluated pre‐mating reproductive barriers between three recently diverged subspecies of Canthon cyanellus (Coleoptera: Scarabaeidae). We further estimated post‐mating barriers in F1 and F2 reciprocal crosses between two subspecies and their contribution to total reproductive isolation (RI). We found that pre‐mating barriers related to mate recognition did not contribute significantly to RI, and that post‐mating, post‐zygotic reproductive barriers were stronger and asymmetrical.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
•Urbanization threatens biodiversity and ecosystem services.•Coprophagous and roller dung beetles were severely affected by urbanization.•Urban forests serve as reservoirs of dung ...beetles.•Urbanization drives the homogenization and impoverishment of dung beetle assemblages.
The maintenance of forest fragments within urban landscapes is essential for human well-being, as the loss of biodiversity may result in a reduction of ecological services in cities. Conserving diverse functional groups within urban landscapes is essential, since it is directly related with the resilience of such ecosystems. Through the use of indicator groups, it is possible to draw predictions on how communities respond to increasing urbanization. The goal of our study was to assess how the increase of urban land cover affects the assemblage and functional groups of dung beetles (Scarabaeinae) that inhabit forest fragments in a tropical city. We sampled dung beetles in nine fragments embedded in the metropolitan region of João Pessoa, Brazil. Increasing urbanization negatively affected the abundance of coprophagous species, as well as the species richness, abundance and biomass of roller beetles. Assemblages from the most urbanized forest fragments were significantly different from the other fragments. According to the decomposition of β diversity, species turnover was the main process shaping the dung beetle assemblages in João Pessoa. In this study we provide evidence that specific functional groups of dung beetles are affected by urbanization. Furthermore, as each functional group has different strategies to occupy habitats and use resources, urbanization has contrasting effects for each group. Our results confirm that dung beetles are highly sensitive to urbanization and that protected areas within cities are fundamental to conserve biodiversity and ecosystem services.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
El decremento en las poblaciones naturales y manejadas de polinizadores ha situado el interés sobre el papel de los polinizadores, principalmente en el sector agrícola, por los efectos reportados en ...lo que se conoce como la “crisis de los polinizadores”. Dentro de los polinizadores más representativos se encuentran las abejas, y dentro de éstas, las abejas sin aguijón (Apidae: Meliponini). Estas últimas tienen gran relevancia ecológica, económica y cultural en el mundo y particularmente en México, por ser un grupo manejado desde hace cientos de años para obtención de miel y otros productos de la colmena. En esta revisión de literatura nos enfocamos en documentar lo que se sabe sobre las abejas sin aguijón en cuanto a su distribución, genética y ecología. En particular nos interesa resaltar aspectos sobre sus interacciones y los servicios ecosistémicos que proveen. Nuestro objetivo fue sintetizar la información disponible para México e identificar áreas de oportunidad en el estudio de estas abejas, con el fin de promover mejores estrategias de conservación y manejo. Encontramos que falta intensificar los estudios de este grupo para poder realizar un análisis de cómo los cambios ambientales afectan la riqueza de especies, abundancia, distribución e interacciones. Así mismo, la falta de estudios longitudinales nos impide conocer la magnitud del declive de estos polinizadores. Finalmente, proponemos incluir en los estudios de ecología y genética de abejas sin aguijón un enfoque de participación social, la cual puede proveer información muy valiosa sobre abejas nativas en México.
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.
The objective of this study was to determine the critical thermal minimum CTmin, critical thermal maximum CTmax, and thermal tolerance range of A. mellifera at three different elevations located in ...the Mexican Transition Zone: 11; 1,324, and 3,304 m.a.s.l. In general, we found that the CTmin of A. mellifera was lower at the site with the highest elevation (i.e., they tolerate colder temperatures). At the same time, the CTmax remained constant across the three studied elevations, revealing higher plasticity for cold tolerance rather than heat. Moreover, we did not find evidence that the body mass of the individuals was associated with their thermal tolerance at any of the three sampled elevations. Our findings suggest processes of local adaptation of A. mellifera populations in environmentally contrasting sites, allowing them to expand their range of distribution, which could be useful in predicting responses to future environmental change.
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.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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