Key Laboratory of Plant Resource Conservation and Sustainable Utilization, South China Botanical Garden, CAS, Guangzhou, China.
Centre for Plant Ecology, CAS Core Botanical Gardens, Guangzhou, China.
J Anim Ecol. 2021 Jul;90(7):1678-1690. doi: 10.1111/1365-2656.13483. Epub 2021 Apr 15.
Plants, phytophagous insects and their parasitoids form the most diverse assemblages of macroscopic organisms on earth. Enclosed assemblages in particular represent a tractable system for studying community assembly and diversification. Communities associated with widespread plant species are especially suitable as they facilitate a comparative approach. Pantropical fig-wasp communities represent a remarkably well-replicated system, ideal for studying these historical processes. We expect high dispersal ability in non-pollinating fig wasps to result in lower geographical turnover in comparison to pollinating fig wasps. The ability of non-pollinating wasps to utilise a number of hosts (low host specificity) is a key determinant of overall geographical range, with intraspecific competition becoming a constraining factor should diet breadth overlap among species. Finally, we expect conserved community structure throughout the host range. We aim to test these expectations, derived from population genetic and community studies, using the multi-trophic insect community associated with Ficus hirta throughout its 3,500 km range across continental and insular Asia. We collect molecular evidence from one coding mitochondrial gene, one non-coding nuclear gene and multiple microsatellites across 25 geographical sites. Using these data, we establish species boundaries, determine levels of host specificity among non-pollinating fig wasps and quantify geographical variation in community composition. We find low host specificity in two genera of non-pollinating fig wasps. Functional community structure is largely conserved across the range of the host fig, despite limited correspondence between the ranges of non-pollinator and pollinator species. While nine pollinators are associated with Ficus hirta, the two non-pollinator tribes developing in its figs each contained only four species. Contrary to predictions, we find stronger isolation by distance in non-pollinators than pollinators. Long-lived non-pollinators may disperse more gradually and be less reliant on infrequent long-distance dispersal by wind currents. Segregation among non-pollinating species across their range is suggestive of competitive exclusion and we propose that this may be a result of increased levels of local adaptation and moderate, but regular, rates of dispersal. Our findings provide one more example of lack of strict codiversification in the geographical diversification of plant-associated insect communities.
植物、植食性昆虫及其寄生蜂构成了地球上最具多样性的宏观生物组合。特别是封闭的组合代表了一个易于研究群落组装和多样化的系统。与广泛分布的植物物种相关的群落特别适合作为比较方法的基础。泛热带榕果小蜂群落是一个非常好的复制系统，非常适合研究这些历史过程。我们预计非传粉榕小蜂的高扩散能力会导致其地理周转率低于传粉榕小蜂。非传粉小蜂利用多种宿主的能力（宿主特异性低）是总体地理范围的关键决定因素，随着种内竞争成为物种间饮食广度重叠时的制约因素。最后，我们期望在整个宿主范围内保持保守的群落结构。我们旨在通过在整个亚洲大陆和岛屿上跨越 3500 公里的榕属植物 Ficus hirta 与其相关的多营养昆虫群落，来检验这些源自种群遗传学和群落研究的预期。我们从一个编码线粒体基因、一个非编码核基因和多个微卫星收集了 25 个地理地点的分子证据。利用这些数据，我们确定了物种边界，确定了非传粉榕小蜂的宿主特异性水平，并量化了群落组成的地理变化。我们发现两种非传粉榕小蜂的宿主特异性较低。尽管非传粉者和传粉者物种的范围之间存在有限的对应关系，但功能群落结构在宿主榕属植物的范围内基本保持不变。虽然有 9 种传粉者与榕属植物 Ficus hirta 相关，但在其榕果中发育的两个非传粉小蜂部落每个部落仅包含 4 种物种。与预测相反，我们发现非传粉者的隔离程度比传粉者更强。寿命长的非传粉者可能会更缓慢地扩散，并且不太依赖于由风向引起的罕见长距离扩散。非传粉物种在其范围内的隔离表明存在竞争排斥，我们提出这可能是由于局部适应水平的提高以及适度但有规律的扩散所致。我们的发现提供了另一个例子，即在与植物相关的昆虫群落的地理多样化过程中，严格的共进化并不存在。
