Lorena Ashworth

Genetic consequences of habitat fragmentation in plant populations: susceptible signals in plant traits and methodological approaches

Conservation of genetic diversity, one of the three main forms of biodiversity, is a fundamental concern in conservation biology as it provides the raw material for evolutionary change and thus the potential to adapt to changing environments. By means of meta‐analyses, we tested the generality of the hypotheses that habitat fragmentation affects genetic diversity of plant populations and that certain life history and ecological traits of plants can determine differential susceptibility to genetic erosion in fragmented habitats. Additionally, we assessed whether certain methodological approaches used by authors influence the ability to detect fragmentation effects on plant genetic diversity. We found overall large and negative effects of fragmentation on genetic diversity and outcrossing rates but no effects on inbreeding coefficients. Significant increases in inbreeding coefficient in fragmented habitats were only observed in studies analyzing progenies. The mating system and the rarity status of plants explained the highest proportion of variation in the effect sizes among species. The age of the fragment was also decisive in explaining variability among effect sizes: the larger the number of generations elapsed in fragmentation conditions, the larger the negative magnitude of effect sizes on heterozygosity. Our results also suggest that fragmentation is shifting mating patterns towards increased selfing. We conclude that current conservation efforts in fragmented habitats should be focused on common or recently rare species and mainly outcrossing species and outline important issues that need to be addressed in future research on this area.

A quantitative review of pollination syndromes: do floral traits predict effective pollinators?

The idea of pollination syndromes has been largely discussed but no formal quantitative evaluation has yet been conducted across angiosperms. We present the first systematic review of pollination syndromes that quantitatively tests whether the most effective pollinators for a species can be inferred from suites of floral traits for 417 plant species. Our results support the syndrome concept, indicating that convergent floral evolution is driven by adaptation to the most effective pollinator group. The predictability of pollination syndromes is greater in pollinator-dependent species and in plants from tropical regions. Many plant species also have secondary pollinators that generally correspond to the ancestral pollinators documented in evolutionary studies. We discuss the utility and limitations of pollination syndromes and the role of secondary pollinators to understand floral ecology and evolution.

Pollination Syndromes: A Global Pattern of Convergent Evolution Driven by the Most Effective Pollinator

Convergent evolution of floral traits driven by pollinators has resulted in floral syndromes shared among different plant lineages. However, the flowers of many plant species are often visited by different pollinator groups, which apparently contradict the idea of syndromes. Here, we demonstrate that the most efficient pollinators consistently correspond to the ones predicted by the syndrome, and the predictive accuracy of the syndrome tends to be higher for species pollinated exclusively by one functional group than for species pollinated by more than one functional group. Secondary pollinator functional groups affected differentially the relative efficiency of the primary pollinator depending of the syndrome. The most frequent secondary pollinator group of a given syndrome is also the least efficient one. Floral symmetry did not influence predictability of pollination syndromes. Except for the bee-syndrome plants, pollination syndromes were more effective on plants that depend strongly on animal pollination than on less dependent plants. Last, effective pollinators for each floral syndrome were better predicted for plants from tropical regions, particularly for the bat, bee, and bird syndromes. Our results have implications on the effects of global change on floral evolution and suggest that current suites of floral traits in most plant species have the potential to adapt to new conditions under changing selective pollination environments.

Human Impacts on Pollination, Reproduction, and Breeding Systems in Tropical Forest Plants

Over the last two decades several studies have shown that plant species of contrasting life-forms ranging from small herbs to large trees may experience a decline in reproductive success following habitat fragmentation and population disruption (Bawa 1990; Aizen and Feinsinger 1994; Aguilar et al. 2006). Such outcome has been shown for many plants throughout the tropics, particularly trees, where human activities have resulted in elevated rates of habitat fragmentation and degradation (Ghazoul and Shaanker 2004; Quesada and Stoner 2004; Quesada et al. 2004). Because almost 90 percent of angiosperms (i.e., flowering plants) depend on animals for effective pollination and sexual reproduction (Buchmann and Nabhan 1996), it is of central concern to understand the capacity of pollinators for transferring pollen among individuals and its consequences on plant reproduction in newly created anthropogenic landscapes.