中国榕小蜂触角感受器形态特征及进化适应性分析

Morphological characteristics and evolutionary adaptation analysis of the antennal sensilla of fig wasps from China

【目的】榕树与传粉榕小蜂体系是协同进化、专性传粉的经典系统,每种榕树上一般还生活有种类丰富、数目众多的非传粉榕小蜂。在选择压力下,榕小蜂为在榕果内生存产生了明显的适应性形态。触角感受器是昆虫通讯系统的单元,其形态是反映生态和进化适应性的最佳特征之一。本文旨在对中国部分传粉和非传粉榕小蜂的触角感受器的形态多样性和进化适应性进行系统研究。【方法】对来源于海南和云南15种榕树上24种榕小蜂54个型的触角感受器形态进行了扫描电镜观察,基于现有的分子系统发育树,对传粉榕小蜂触角感受器的形态特征进行了性状演化分析,并对榕小蜂的形态特征进行了进化适应性分析。【结果】榕小蜂触角感受器普遍存在雌雄二型现象。雌蜂触角感受器种类有毛状、锥状、板状、刺状、钟形、腔锥状和栓锥状等,数目丰富,并且进果产卵的传粉雌蜂和果外产卵的非传粉雌蜂之间、进果产卵的传粉雌蜂和进果产卵的非传粉雌蜂之间在形态上存在差异。传粉雄蜂和不具有雄性多型现象的非传粉雄蜂触角感受器极为退化,具有雄性多型的非传粉雄蜂触角感受器形态在种内不具有显著差异。性状演化分析表明进化路径相当复杂,可能存在多次独立进化过程。触角感受器的形态类型与其进化适应性相关。【结论】榕小蜂触角感受器类型多样,形态变化丰富,并为适应榕果内的生存而产生了进化适应性特点。雌蜂和雄蜂在榕果内受到了完全不同的选择压力,行使不同的生态功能,从而产生了不同的适应性形态。不同的适应性形态可能与雌蜂不同的产卵行为、雄蜂不同的交配策略具有一定联系。该文是首次对中国榕小蜂触角感受器形态进行系统研究的报道,有助于更好地理解榕小蜂的形态特征、进化路线、行为策略和生态关系。

[ Aim ] The interaction between figs and their pollinating fig wasps represents a classic system of co-evolution and mutualism. In addition, there are various species of non-pollinating fig wasps living on each fig species. Under the selective pressure of living within fig syconia, the fig wasps have evolved many adaptive morphological characteristics. Antennal sensiflum, as the unit of communication system of fig wasps, is one of the best morphological characteristics to reflect the evolutionary adaptation. This study aims to investigate the morphological diversity and evolutionary adaptation of the antennal sensilla of fig wasps. [ Methods ] Fifty-four types of 24 species of fig wasps on 15 fig species from Hainan and Yunnan provinces, China were selected as the materials. The morphology of antennal sensilla of these species was observed by the scanning electronic microscope. Based on the molecular phylogeny tree, the character evolution of the antennal sensilla was analysed, and the evolutionary adaptation of morphological characteristics was discussed. [ Results ] Our results show that the extremely sexual dimorphism of the antennal sensilla exists in most species of fig wasps. There are differences in the morphological characteristics of the antennal sensilla between the pollinators and the non-pollinators ovipositing outside the fig syconia and also between the pollinators and the non-pollinators ovipositing inside the fig syconia. The morphological characteristics of the antennal sensilla of the pollinating males and the non-pollinating males without male polymorphism are much degenerated. The morphological characteristics of the antennal sensilla among the non-pollinating males with male polymorphism do not show significant difference. Character evolution analysis of the types of the antennal sensilla reveals the multiple independent evolution of these morphological characteristics and the relationship with evolutionary adaptation. [ Conclusion ] The diversity of the antennal sensilla of fig wasps are very rich, revealing the diagnostic characters for evolutionary adaptation. Due to the different ecological pressures and functions for males and females, they evolved different adaptive characteristics, which correlate with different oviposition behaviors of females and with different mating strategies of males. Our study provides new insight on the morphological adaptation, evolutionary trend, behavioral strategies, and ecological relationship of fig wasps.