Morphological traits and bioindicators: a case study on dung beetles in the Maputaland Centre of Endemism.

Dung beetles have been identified as important indicators of habitat change in the Maputaland centre of Endemism, an area of southern Mozambique and northern Kwazulu-Natal in South Africa. Maptutaland harbours one of the rarest vegetation types, sand forest, of which only small portions are currently protected in four conservation parks of South. Sand forest habitats are rapidly undergoing transformation due to increasing elephant browsing activities that create a sand forest-mixed woodland matrix. It has been observed that dung beetle assemblages are significantly different in sand forest and mixed woodland habitats, and if elephant activity continues in sand forest patches, it is predicted that dung beetle assemblages will become more homogenous across habitats. Two habitats, namely undisturbed sand forest and mixed woodland, were sampled and I investigated the morphological differences (wing loading and aspect ratio) of wings across habitats using generalists and indicator species. Low wing loading combined with a high aspect ratio enhances lift production and take-off ability with a mechanical power output improving dispersal abilities in mixed woodland indicator species compared to sand forest indicators. Conversely, predictions regarding generalist species were rejected because they had overall similar wing morphology across habitats. Furthermore, if fragmentation of sand forest patches is not managed, dung beetles are expected to become constrained by their wing morphology and a homogeneous arthropod assemblage will occur across habitats. This could jeopardize long-term studies which use dung beetles to monitor the biodiversity and ecosystem functioning in the MC.蜣螂已被证实为马普塔兰特有中心（Maputaland Centre of Endemism）生境变化的重要指示类群，该区域涵盖莫桑比克南部与南非夸祖鲁-纳塔尔省北部片区。马普塔兰拥有全球最珍稀的植被类型之一——沙地森林（sand forest），目前仅少量片区在南非的4座保护公园中得到保护。受大象取食活动加剧影响，沙地森林生境正快速发生演替，逐渐形成沙地森林-混生林地的镶嵌格局。已有研究观测到，沙地森林与混生林地生境中的蜣螂类群组成存在显著差异；若大象仍持续在沙地森林片区活动，预计不同生境中的蜣螂类群组成将逐渐趋于同质化。本研究选取未受干扰的沙地森林与混生林地两类生境开展采样，并利用广食性物种与指示物种，分析了不同生境下蜣螂的翅膀形态差异（翼载荷与展弦比）。相较于沙地森林指示物种，混生林地指示物种的翼载荷更低且展弦比更高，这一翅膀形态特征可提升升力产生与起飞能力，通过优化机械功率输出增强其扩散能力。与之相反，针对广食性物种的预测未得到验证——这类物种在两类生境中的翅膀形态整体并无显著差异。此外，若不对沙地森林片区的破碎化问题加以管控，蜣螂将受限于其翅膀形态特征，最终导致不同生境中的节肢动物类群组成趋于同质化。这将对以蜣螂为指示类群，监测马普塔兰特有中心生物多样性与生态系统功能的长期研究造成严重威胁。