Unexpectedly diverse forest dung beetle communities in degraded rain forest landscapes in Madagascar

Kaisa Anneli Torppa,Helena Wirta,Ilkka Hanski

doi:10.1111/btp.12767

Kaisa Anneli Torppa, Helena Wirta + Show 1 more

Open Access

https://doi.org/10.1111/btp.12767

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Abstract

AbstractTropical forests, which harbor high levels of biodiversity, are being lost at an alarming speed. Madagascar, a biodiversity hotspot, has lost more than half of its original forest cover. Most of the remaining forests are small fragments of primary and secondary forest with differing degrees of human impact. These forests, as well as coffee and fruit plantations, may be important in supporting the forest‐dependent biodiversity in Madagascar but this has been little studied. In Madagascar, dung beetles, which offer important ecosystem services, are largely restricted to forests. We examined the ability of fragmented and degraded forests to support dung beetle diversity, compared to the large areas of primary forest in eastern Madagascar. We found a general trend of a reduction of species with a loss of forest connectivity. In contrast, a higher level of forest disturbance was associated with higher species diversity. In several sites of low‐quality forest as many or more species were found as in less disturbed and primary forests. The average size of dung beetles was smaller in the lower quality localities than in the primary forests. These findings suggest that many forest dung beetles in Madagascar are better adapted to forest disturbance than earlier expected, although they require some level of connectivity to surrounding forest.Abstract in Malagasy is available with online material.

Highlights

Tropical forests, which contain high levels of the biodiversity on Earth (Lovejoy, 1997), are declining fast (Hansen et al, 2013)
What remains are selectively logged tropical forests (Asner, Rudel, Aide, Defries, & Emerson, 2009) and landscapes that are mosaics of remnant forest patches and low-intensity cultivations (Daily, 1997). These may retain a substantial part of the more generalist species, but a large part of the original forest biodiversity will be lost (Barlow et al, 2016; Gibson et al, 2011)
Lack of the large species Epilissus prasinus, E. emmae obscuripennis, and Nanos bimaculatus in zones I–V is due to the regional turnover in species composition (Figure 2) and explains the negative effect of altitude on average body size (Table 4)

Summary

| INTRODUCTION

Tropical forests, which contain high levels of the biodiversity on Earth (Lovejoy, 1997), are declining fast (Hansen et al, 2013). In addition to habitat size, vegetation quality (Lee, Lee, Lim, Huijbregts, & Sodhi, 2009; Nichols et al, 2007; Shahabuddin et al, 2010; Slade, Mann, & Lewis, 2011) and presence of resource providing mammals are important in determining dung beetle species richness and community structure in degraded forests (Bogoni et al, 2016; Estrada, Anzures, & Coates-Estrada, 1999; Nichols, Gardner, Peres, & Spector, 2009). What is the level of dung beetle species richness within fragmented and degraded humid forests in Madagascar? Second, are there systematic differences in the dung beetle species and community composition between degraded forest landscape and primary forest areas?

| MATERIAL AND METHODS

Ranomafana

Vatovavy

| DISCUSSION

Findings

| CONCLUSIONS