Population ecology and behaviour of two Afrotropical forest butterflies

Abstract

Over the last decades, numerous natural habitats have been converted into settlement areas, agricultural land, and tree plantations on a large spatial scale. As a result, natural ecosystems have been destroyed. In consequence, many ecosystems exist today as small and geographically isolated remnants. To what extent the original species diversity can persist in such small habitat patches is questionable and strongly depends on the ecology of the species. A prominent example of severe habitat destruction are the species-rich tropical cloud forests of Taita Hills in southern Kenya, which have been deforested almost completely during past decades. However, there still exist typical forest species in the few remaining forest fragments. In this study, we investigate the population ecology and behaviour of two butterfly species present in the cloud forest remnants of Taita Hills, Protogoniomorpha parhassus and Precis tugela. Over a period of one month, we conducted Mark-Release-Recapture to study population sizes and demographic structures, lifespan, dispersal, and behaviour. We found that both species exhibited medium population sizes and are sedentary. However, some individuals performed dispersal throughout the forest. The behaviour of the two species differs: While P. tugela was mostly observed basking with open wings, P. parhassus was mostly sitting under leaves with closed wings. The life span was rather long for butterflies. Implications for insect conservation This study documents the population ecology and behaviour of these two Afrotropical butterflies and underlines the relevance of the conservation of cloud forest remnants to preserve species, which mainly depends on these habitat remnants.

Habitat specialisation and resource availability determine dispersal behaviour in four afro‐tropical butterflies

“…In contrast to the temperate regions where many MRR studies have already been performed and were we have a relatively good picture of the dispersal power of butterflies representing a large array of ecologically different species, our knowledge on East African butterflies in this respect is still very limited. The very low dispersal capacity of all butterfly species analysed in this study and the high dispersal observed in two large forest butterfly species in the humid mountain forests of Taita hills in southern Kenya (Habel et al, 2023)…”

“…In addition, due to their high site fidelity, such species can only reach a new potential habitat with difficulty and are thus often subject to stochastic extinction processes, which occur more frequently in small and isolated populations than in large and interconnected ones (Melbourne & Hastings, 2008). Looking at the larger distance estimates for our four study species, their dispersal power was low if compared with butterfly species from Kenyan mountain forests (Habel et al, 2023), but also in comparison with temperate Central Europe (Ehl et al, 2019, Fric et al, 2010, Junker et al, 2021, Konvickova et al, 2023, Pennekamp et al, 2014, Zimmermann et al, 2005. In general, the extrapolated dispersal probabilities over larger distances based on NEFs were implausibly low in all four species and for all three distance classes used (i.e., 20, 30, 50 m), a more general fact as pointed out already by Baguette (2003).…”

“…These findings correspond with previous data on forests and open land butterfly species (Namu et al, 2008). Thus, other afro-tropical forest butterflies are also strongly restricted to and mostly remain within their habitats (Borghesio & Wagura, 2014;Habel et al, 2023;Nyafwono et al, 2014), which are characterised by specific abiotic and biotic conditions, such as humid and cool microclimates as well as specific habitat structures (Habel et al, 2013) et al, 2013). In contrast, numerous afro-tropical savannah species are much more opportunistic in the choice of their habitats (Habel et al, 2018;Larsen, 1991;Schmitt et al, 2020;Scriven et al, 2017) and their assumed dispersal ranges from highly sedentary to migratory (Larsen, 1991).…”

“…These findings correspond with previous data on forests and open land butterfly species (Namu et al, 2008). Thus, other afro‐tropical forest butterflies are also strongly restricted to and mostly remain within their habitats (Borghesio & Wagura, 2014; Habel et al, 2023; Nyafwono et al, 2014), which are characterised by specific abiotic and biotic conditions, such as humid and cool microclimates as well as specific habitat structures (Habel et al, 2013). Consequently, they only rarely leave forests and bridge open landscapes (but see Konvicka et al, 2008 for an exception from temperate regions).…”

“…Consequently, they only rarely leave forests and bridge open landscapes (but see Konvicka et al, 2008 for an exception from temperate regions). Nevertheless, the dispersal potential of forest species is often intermediate to high, for tropical and temperate species likewise—but restricted to inside forests (Cassel‐Lundhagen & Sjögren‐Gulve, 2007; Fric & Konvicka, 2007; Habel et al, 2023; Konvicka et al, 2008; Vlasanek et al, 2013). In contrast, numerous afro‐tropical savannah species are much more opportunistic in the choice of their habitats (Habel et al, 2018; Larsen, 1991; Schmitt et al, 2020; Scriven et al, 2017) and their assumed dispersal ranges from highly sedentary to migratory (Larsen, 1991).…”