The evolution of the Lepilemuridae-Cheirogaleidae clade
- Authors: Andrews, Curswan Allan
- Date: 2019
- Subjects: Lemurs
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/40216 , vital:35989
- Description: The Lepilemuridae and the Cheirogaleidae, according to recent molecular reconstructions, share a more recent common ancestor than previously thought. Further phylogenetic reconstructions have indicated that body size evolution in this clade was marked by repeated dwarfing events that coincided with changes in the environment. I aimed to investigate the morphological implications of changes in body size within the Lepilemur-cheirogaleid clade, testing four predictions. Together with Dr. Couette, I collected data on the overall palate shape and predicted that shape is likely to be influenced by several factors including phylogeny, body size and diet. Geometric morphometric analyses revealed that, although a strong phylogenetic signal was detected, diet had the major effect on palate shape. In a similar vein, when examining the arterial circulation patterns in these taxa, I predicted that changes in body size would result in changes and possible reductions in arterial size, particularly the internal carotid artery (ICA) and stapedial artery (SA). Analyses with micro-computed tomography (CT) and 3D imaging indicated that changes in body size led to reduction of a functional stapedial artery in Lepilemur, making it an intermediate stage between the daubentoniid, lemurid and indriid species with large stapedial arteries, and the smaller bodied cheirogaleids with an alternative blood supply in the form of an enlarged ascending pharyngeal artery. Lepilemur is the smallest living folivorous primate, and likely to be at the threshold body size to be able to subsist on such a poor diet. To investigate shifts in dietary patterns that accompanied changes in body size, I chose to explore the reported behaviour of caecotrophy as a possible means for the sportive lemurs to derive additional nutrient from their food sources. I predicted that, if caecotrophy is a way to assist folivory at small body size, the energy contained in “caecotrophic” and latrine faecal samples should be different. Analyses showed significant iv differences between the two types of faeces and, combined with an analysis of faecal bacterial diversity, support the occurrence of caecotrophy. Finally, I compared the digestive efficiency of two small, distantly related gummivorous primates that evolved their diets convergently. I studied the digestion of gum in Microcebus griseorufus and compared this with gum digestion in Galago moholi. I predicted that an evolutionary disposition to fermentation inherited from a folivorous ancestor would aid in the digestion of gum in mouse lemurs. Results indicated that retention time was prolonged by the presence of secondary compounds in Microcebus fed with Commiphora gum but relatively shorter (< 24 hrs) when fed Alantsilodenron gum, a preferred food. Despite the fact that G. moholi has an ansa coli, which is missing in M. griseorufus species, both are highly efficient at digesting gum. These data provide some of the first indicators of how dietary changes from a larger-bodied folivorous ancestor to partially gummivorous, small-bodied descendants may have occurred in evolutionary time.
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- Date Issued: 2019
A comparative evolutionary approach to gum-feeding in Galago Moholi and Microcebus Griseorufus
- Authors: Andrews, Curswan Allan
- Date: 2014
- Language: English
- Type: Thesis , Masters , MSc (Zoology)
- Identifier: vital:11795 , http://hdl.handle.net/10353/d1019831
- Description: Gums are soluble plant exudates rich in complex carbohydrates. In primates, the consumption of gum (gummivory) has been described as a primitive, fall-back diet exhibited when other food sources become scarce, particularly during dry periods. In apparent support for this interpretation, gummivory is often observed in nocturnal strepsirhines (tooth-combed primates) believed to have retained many primitive features. The complex carbohydrates in gums, however, are also known to be difficult to digest, and require particular alimentary adaptations. The hypothesis of a primitive diet predicts that gummivorous strepsirhines should use homologous digestive strategies, while the presence of different digestive adaptations in different lineages would suggest convergent evolution. I compared the digestive adaptations to gummivory in two small strepsirhine taxa, African lesser bushbabies (Galago moholi) and Malagasy reddish-grey mouse lemurs (Microcebus griseorufus). Both taxa digest gum primarily by fermentation, and have enlarged caeca for this process, but only G. moholi has an ansa coli in which digestion can be continued. In captive feeding experiments, the faeces of wild-caught G. moholi and M. griseorufus showed no significant difference in their digestive efficiency of gum compared with a control food (banana), and the banana and gum samples showed no significant difference in nutrient concentration and overall composition. To gain a broader understanding of the origins of gummivory in strepsirhines, I used a phylogenetic method to reconstruct their dietary evolution. My results indicate that gummivory evolved convergently in several primate lineages, apparently in response to environmental hypervariability. I conducted biochemical analyses of the secondary compounds found in gums that are regularly consumed, and preliminary results show that Commiphora spp. have a number of compounds, while Acacia spp. show no such traces. The absence of secondary compounds from M. griseorufus faeces suggests that the animals have physiological means for either converting them into digestible products or detoxifying and excreting them in their urine. Finally, I compared the distribution patterns of G. moholi and M. griseorufus with climatic parameters; both study taxa inhabit regions in which the dry season is characterised by little to no rainfall, a drought that may persist for months. Similar climatic regions are occupied by other gum-feeders, including the marsupial gliders (Petauridae) of Australia.
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- Date Issued: 2014