Ecological fragmentation effects in mouse lemurs and small mammals in northwestern Madagascar

Abstract

Habitat loss and fragmentation are major ecological forces threatening animal communities across the globe. These issues are especially true in Madagascar, where forest loss is ongoing. We examined the effects of forest fragmentation on the distribution and abundance of sympatric, endemic gray, and golden-brown mouse lemurs (Microcebus murinus and Microcebus ravelobensis), the endemic western tufttailed rat (Eliurus myoxinus), and the invasive black rat (Rattus rattus) in two regions in northwestern Madagascar. We used systematic capture procedures in 40 forest fragments and four continuous forest sites which differed in size, shape, and degree of isolation. With a trapping effort of 11,567 trap nights during two dry seasons (2017-2018), we captured 929 individuals (432 M. ravelobensis, 196 M. murinus, 116 E. myoxinus, and 185 R. rattus). We examined the influence of study region, forest type (fragment vs. continuous), forest size, forest shape, the proportion of 50-m forest edge and distance to continuous forest on the abundance and interaction of the four species. Responses to fragmentation differed strongly between species, but no interaction could be detected between the abundance of the different species. Thus competition within and between native and invasive species may not be regulating abundances in these regions. On the contrary, the abundance of M. ravelobensis and E. myoxinus differed significantly between study regions and was negatively affected by fragmentation. In contrast, there was no evidence of an impact of fragmentation on the abundance of M. murinus. Finally, the invasive R. rattus responded positively to the increasing distance to the continuous forest. In conclusion, the response of small Malagasy mammals to forest fragmentation varies largely between species, and fragmentation effects need to be examined at a species-specific level to fully understand their ecological dynamics and complexity. K E Y W O R D S abundance, edge effect, Eliurus, Forest fragmentation, Madagascar, Microcebus, Rattus

Effects of habitat edges on vegetation structure and the vulnerable golden-brown mouse lemur (Microcebus ravelobensis) in northwestern Madagascar

“…A high ecological flexibility of this lemur species towards variable ecological conditions at forest edges may explain such seemingly contradictory responses, and also its occurrence in several different types of microhabitats [36]. Such a flexibility may enable this species to cope with disturbances and some anthropogenic habitat changes within forests [63], although they seem to respond negatively to habitat fragmentation per se, probably due to a limited potential to connect between fragmented forest patches across open space [37]. Further studies are urgently needed to evaluate the critical features of landscapes that are needed to sustain viable populations of this vulnerable lemur species.…”

“…M. ravelobensis forms mixed-sex sleeping groups and sleeps in tree-holes but also in dense tangles of lianas, leaves or self-built nests [38,39]. Previous studies reported certain microhabitat preferences of this species, such as habitats containing higher density of trees with many lianas and a higher cover of the herb layer, and habitats closer to surface water or at lower altitudes [36,37,40,41]. Most recently, significant regional differences were revealed in the abundance of M. ravelobensis across its distribution [37].…”

“…Previous studies reported certain microhabitat preferences of this species, such as habitats containing higher density of trees with many lianas and a higher cover of the herb layer, and habitats closer to surface water or at lower altitudes [36,37,40,41]. Most recently, significant regional differences were revealed in the abundance of M. ravelobensis across its distribution [37]. Whether these differences correspond to differences in edge responses, however, is not yet known.…”

“…Our study focused on the vulnerable M. ravelobensis which has a limited geographic distribution in the dry deciduous forests of northwestern Madagascar [34,35]. M. ravelobensis is a nocturnal, small-bodied (~ 60 g), arboreal, omnivorous solitary forager and occurs in partial sympatry with M. murinus in some but not all forests of northwestern Madagascar [36,37]. M. ravelobensis forms mixed-sex sleeping groups and sleeps in tree-holes but also in dense tangles of lianas, leaves or self-built nests [38,39].…”

Pedigree-based measurement of thede novomutation rate in the gray mouse lemur reveals a high mutation rate, few mutations in CpG sites, and a weak sex bias

“…Mouse lemurs comprise a radiation of morphologically cryptic primates distributed throughout Madagascar (Hotaling et al, 2016). Numerous studies have suggested that their rapid speciation dynamics may reflect climatic change through time in Madagascar (Andriatsitohaina et al, 2020;Setash et al, 2017) and that their unique life history characteristics make them an ideal genetic model organism (Ezran et al, 2017;Hozer et al, 2019). Thus, an accurate mutation rate estimate for these organisms can potentially yield valuable insight into both geological and biological phenomena.…”