By Jorian A. Hendriks (Maastricht University), Siti Maimunah (Faculty of Forestry, Instiper Yogyakarta), Mariaty (Universitas Muhammadiyah Palangakaraya) and Mark E. Harrison (University of Exeter), based on a recent open access paper published by our team in Ecologies (available open access here).
Understanding the causes shaping species richness, abundance, and distribution patterns has taken on a new urgency as a plethora of extant species, many of which are still undescribed and their role in their ecosystem not understood, are experiencing a drastic decline because of human activities. Borneo is a priority area in this context, given its rich biodiversity and historically high rates of forest loss. However, to understand what shapes species-specific patterns across a landscape of diverse habitat types, we first require an understanding of how taxa interact with and respond to changes in their environment. We used Odonata as our focus taxon, which includes both dragonflies and damselflies (Figure 1).
Borneo has the highest number of described Odonata species (~400), of which a remarkable 48% appear to be Bornean endemics.
Odonata are also relatively easy to sample, inhabit a wide range of biotopes, adopt a biphasic lifecycle, and are important to the conservation science community due to their potential to act as ecological disturbance indicators.
Figure 1. Basic anatomy and morphological differences between a dragonfly (bottom) and a damselfly (top). Dragonflies are often distinguished by their thicker bodies and broader wings, while damselflies are easily distinguished by their long and slender bodies with smaller and tender wings. Image retrieved from: ttp://azdragonfly.org/external-anatomy.
Odonata are also very well-researched globally. For example, habitat characteristics such as shade, vegetation structure, and water have been revealed to be primary drivers shaping and influencing Odonata community patterns (species diversity, abundance, and distribution). This is because shade influences the amount of light reaching the forest floor thereby affecting in-water characteristics which, combined with the presence or absence of surface water, influences Odonata reproduction. Meanwhile vegetation structure influences predator-prey interactions, thermoregulation, dispersal ability, breeding, and oviposition site-selection.
Additionally, Odonata body size is strongly associated with thermoregulatory requirements and dispersal ability. As a result, understanding the interplay between habitat characteristics and odonata traits such as thermoregulation and dispersal ability will not only form a basis to understand their behavioral and distribution patterns, but may also be important in understanding their environmental tolerance and resource use patterns.
With this in mind, our team set out to conduct the first research investigating the relationship between morphology and species distribution, diversity and abundance patterns of Odonata communities within the 4910-ha Mungku Baru Education Forest (KHDTK), a lowland heath mosaic forest in Central Kalimantan, Indonesia. This landscape is characterized by undulating topography and is comprised of three main habitat-types: low pole peat swamp, mixed peat-swamp (including riverside areas), and heath forests (known locally as kerangas). The landscape remains largely unprotected and is threatened through mining, timber concessions, and conversion to oil palm and agriculture. We tested the following hypothesis:
Odonata species richness and abundance would differ between the three habitat-types studied;
Species richness and abundance patterns would be influenced by biotic characteristics such as canopy cover and vegetation, and abiotic characteristics such as light intensity and surface water; and
Morphological characteristics (body length, thorax size, and hind wing length) of species assemblages would differ between habitat-specific communities.
Figure 2. (Top) Jorian Hendriks and Pak Viktor recording data on habitat variables and morphological traits of Odonata. (Below) The KHDTK research camp at the time of our surveys (a new, enhanced camp is currently being constructed at the site). Pictures from Jorian Hendriks (top) and Borneo Nature Foundation (bottom).
The results of this study are detailed in a recent paper led by Maastricht University and Universitas Muhammadiyah Palangka Raya in Indonesia. This was published in Ecologies and can be found here.
We found that Odonata diversity, abundance, and distribution patterns were shaped by a number of factors such as habitat characteristics, body size induced eco-physiological constraints and the presence of specialists; with each habitat’s Odonata community assemblage supporting its own unique set of dominant species. Odonata species diversity and abundance was very low in heath forests, but heath habitat appears to be favourable for shade-loving stenotopic (able to tolerate narrow range of ecological conditions) Bornean endemics. Further, we found that morphological traits associated with increased dispersal and larger range size (i.e., thorax and hindwing/body length ratio), influenced suborder (i.e., Anisoptera (dragonfly) and Zygoptera (damselfly)) habitat selection patterns. Odonata that had larger thoraces and showed larger hindwing length to body length ratios selected more for still water habitats such as forest pools (lentic), while Odonata that had smaller thoraces and showed smaller hindwing length to body length ratios selected more for flowing water habitats such as streams (lotic). This finding was in accordance with previous research which suggested that thelarger morphology of dragonflies allows them to inhabit more open and still water habitats, while damselflies prefer to inhabit shaded and flowing water habitats.
Figure 3. A photo plate of a few sampled species: (A) Amphicnemis triplex (male) (B) Rhyothemis obsolescens (male), (C) Vestalis amoena (male), (D) Pachycypha aurea (female), (E) Neurothemis fluctuans (male), (F) Ceriagrion sp.; one of the species of damselfly captured in low pole peat swamp and present in high abundance, and which is a new species to science. Photographs: Jorian Hendriks.
Despite the habitat types being so closely located to each other, strong local habitat dynamics do exist at the site, with the mosaic of different habitat-types supporting a greater species diversity and abundance of Odonata than one habitat alone could harbour. This in turn leadsto different habitat selection strategies and resource use patterns ithin the Odonata community.
This was the first research investigating Odonata communities in this biodiverse region of Borneo, highlighting how under-represented heath forests are in the scientific literature for this region.
The findings of this study suggest that heterogenous areas like the Rungan landscape, which provide a mosaic of different habitats supporting more diverse communities of fauna such as Odonata, are very important to protect. This may be especially the case for taxa with high levels of island endemicity, as exemplified by Borneo’s Odonata.