Abstract
The impacts of forest fragmentation on both reproductive biology and genetic diversity of native plant species is hardly understood, despite some studies have analyzed this current worldwide problem. Since this constitutes one of the main threats to seasonal semi-deciduous forests in Southeastern Brazil, we investigated the reproductive success and the genetic diversity of a distylous, understory shrub (Psychotria hastisepala) within this context of forest fragmentation. For this study, a set of seven forest fragments of sizes ranging from 4.1 to 168.7 hectares were chosen. The intervenient matrix comprised pastures (25-50%), monocultures (33-50%) and rural roads and buildings (14-28.5%). Overall, 91 plants (54 for the short-styled morph and 37 for the long-styled morph; mean of 6.5 plants per fragment) were investigated. To evaluate reproductive success, we quantified fruit and seed production under natural pollination; to evaluate genetic diversity and population structure, we employed ISSR markers on genomic DNA. Plants with the short-styled morph exhibited a significantly higher reproductive success than those with the long-styled morph; there was no association between seed production and size of the forest fragment. Levels of genetic diversity were positively associated with the number of plants per fragment; but they were not related to flower morph. AMOVA showed that about 65% of the overall genetic variation was attributed to the differences between plants within fragments. The results suggested that populations of P. hastisepala were susceptible to decline owing to forest fragmentation.
Highlights
2010) and population size of native species (Aizen & Feinsinger, 1994)
This study addressed the following questions: a) Do floral morphs of P. hastisepala (S or L) differ on reproductive success? b) Is there any association between reproductive success rates and size of forest fragments? c) How is genetic diversity partitioned within and among forest fragments? d) Is reproductive success linked to genetic diversity? Our study took into consideration the context of recent human-led fragmentation which presently dominates the Atlantic Forest of Southeastern Brazil
Our data showed that there were instances in which small fragments harbored large populations of P. hastisepala, whereas large fragments contained a small number of plants
Summary
2010) and population size of native species (Aizen & Feinsinger, 1994). When compared to continuous forests, isolated forest fragments harbor low levels of genetic diversity owing mostly to limited gene flow and genetic drift (Frankham, Ballou & Bruno, 2002). Conservation measures for distylous species will be more effective when genetic diversity within and among remnant populations are understood within the context of forest fragmentation. Our study took into consideration the context of recent human-led fragmentation which presently dominates the Atlantic Forest of Southeastern Brazil. This study addressed the following questions: a) Do floral morphs of P. hastisepala (S or L) differ on reproductive success? Addressing these questions should shed light on causes that render populations of a distylous species, such as P. hastisepala, more susceptible to local extinction when exposed to a scenario of forest fragmentation. Our study contributes to the elaboration of strategies to protect a threatened ecosystem that strongly requires conservation measures
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