Madagascar: a Megadiversity Country

In this short article on lemurs I give a concise introduction for non-specialists to these conspicuous and unique animals on the island of Madagascar. INTRODUCTION Madagascar has long been known for its exquisite wildlife. It has been identified as a Megadiversity country and “Hottest Hotspot” for biodiversity conservation (Meyers et al. 2000 Mittermeier et al. 2005) due to the combination of extraordinary high diversity and extreme degree of threat. Lemurs, a natural group of primates endemic to Madagascar, are possibly the most conspicuous and most widely known wildlife of Madagascar. In this article, written for a non-specialist audience, I try to situate these mammals in a wider context to shed light on (i) their biological position and diversity, (ii) some biological pecularities, and (iii) the important role they may play for Malagasy conservation and development. MADAGASCAR: A MEGADIVERSITY COUNTRY Madagascar is located almost entirely within the tropics. This geographic location with its typical wind regime (trade winds, monsoon. Donque 1975), combined with a north south mountain chain reaching heights up to 2000 m and more allows for year long orographic precipitation on the eastern side, and prolonged dry periods with a distinct rainy season in the wide western lowlands. Combined with the long geological isolation from large continental landmasses but occasional non-synchronized colonisation events by mammals this provides the coarse scenario for the evolution of Madagascar’s mammal wildlife (Goodman and Beanstead 2003, for a comprehensive overview). Due to this particular combination (geographic position, relief, geology, long isolation, occasional colonization) the fauna of Madagascar (biodiversity in general) evolved tremendous endemism. MADAGASCAR’S MAMMAL COMPOSITION On a high systematic level, eight placental mammal orders are present on Madagascar (without cetaceans), whereas 15 are present in continental Africa, 15 in Asia, and 11 in the Americas out of 19 orders globally (Figure 1). The composition is, however, very special. There are on average less genera per animal order in Madagascar (8.1 genera/order) than on other continents. One order of Malagasy mammals, Bibymalagasia, is entirely restricted to Madagascar and went extinct only relative recently (MacPhee 1994) along with artiodactyle pygmy hippos and other large vertebrates (Burney 2004). Within Malagasy mammals, the mammal order primates clearly stands out with the endemic lemurs. The lemurs are the most diverse mammal group on the generic level, and Madagascar is the only place where primates genera are the dominant group overall. On a global scale primates rank 5th behind rodents, bats, carnivores, and even toed hoofed mammals. MADAGASCAR: A HOTSPOT FOR CONSERVATION A biodiversity hotspot is a region that contains at least 0.5 % (or 1,500) of the world’s 300,000 plant species as endemics and has lost 70 % or more of its primary vegetation. Madagascar harbours around 12,000 plant species of which about 9,700 or 3.2 % of the world’s plant species are endemic. An enormous 90 % of the primary vegetation has been lost (Myers et al. 2000). This qualifies Madagascar obviousely as a biodiversity hotspot. Additionally, the consideration of five key factors, endemics and endemic species/area ratios for both plants and vertebrates and habitat loss ranks Madagascar in all figures among the top ten hotspots, along with the Philippines and Sundaland. Hence these regions are also called “hottest hotspots” (Myers et al. 2000). How did Madagascar achieve this position? Madagascar was one of the last great habitable land masses settled by humans. According to the comprehensive review by Burney et al. (2004), multiple points of evidence date the earliest presence of humans at ca. 350 yr BC. A decline in megafauna at around 230-410 AD is followed by large increases in charcoal particles in sediments signalling increased human impact on the landscape. When Madagascar was discovered by Europeans in 1500, almost all of the Malagasy megafaua pygmy hippos, elephant birds, giant tortoises, large lemurs had already disappeared. This was the result of the synergistic combination of human impact, nonlinear natural responses and environmental change, population fragmentation, and local extirpation (Burney et al. 2004). Today, the same negative synergies of resource overutilization, fire mediated vegetation change, and biological invasion combined with an enormously growing FLAGSHIPSPECIES Lemurs Ambassadors for Madagascar Urs Thalmann I, II Anthropological Institute University Zurich-Irchel Winterthurerstrasse 190 CH–8057 Zurich, Switzerland Phone: +41 44 6354192 Fax: +41-44-635 68 04 E-mail: [email protected] I ANTHROPOLOGICAL INSTITUTE, UNIVERSITY ZÜRICH-IRCHEL, SWITZERLAND II JANE GOODALL INSTITUTE SWITZERLAND MADAGASCAR CONSERVATION & DEVELOPMENT VOLUME 1 | ISSUE 1 — DECEMBER 2006 PAGE 5 population continue, pulling smaller lemur species and a host of other organisms into the extinction vortex. WHAT ARE LEMURS? Lemurs (Lemuriformes) are one of the six natural groups of primates and occur only in Madagascar (Figure 2). On the nearby Comoros they have been introduced from Madagascar (Pastorini et al. 2003). The Afro-Asian Loriformes (lorises and bushbabies) are the closest relatives. Together these primates constitute the strepsirrhine group that encompasses primates with a “wet” nose and other common characteristics. The name refers to the morphology of the nose with an outer rhinarium and a midline cleft, as for example in cats and dogs. Conversely, Southeast Asian tarsiers, New World Monkeys, Afro-Asian Old World Monkeys, apes and humans are considered as a group apart, the haplorrhines. There are several characteristics that distinguish strepsirrhines and haplorrhines as well as the different groups. The eye of most lemurs, the lorises and galagos, for example, have a reflective layer in the eye as have many other mammals. This reflecting layer facilitates finding them at night. This layer is not developed in haplorrhine primates. Strepsirrhine and haplorrhine primates are distinguished by many other morphological, physiological and anatomical characters. These are not presented here but can be found in text books on primatology (e.g., Fleagle 1999). Today, 15 lemur genera representing 5 zoological families still survive, whereas at least 8 genera representing 3 families have disappeared in pre-historic time. A major role has been attributed to the arrival of human settlers on the island as trigger for the extinction of these lemurs (Burney et al. 2004). Large, diurnal lemurs were especially prone to extinction. Today, the largest surviving diurnal lemurs reach a body mass of approximately 7.5 kg (eastern Propithecus and Indri). All extinct diurnal lemur genera had a higher body mass, the largest may have reached a body mass of 150-200 kg (Figure 3). HOW MANY LEMUR SPECIES EXIST? The number of lemur species has dramatically increased over the past 15 years (Figure 4). Whereas Mittermeier et al. (1994) counted 32 species in the first edition of their lemur guide, this number has more than doubled. My current compilation reaches 71 species (based on Mittermeier et al. 2006, Andriaholinirina et al., 2006, Louis et al. 2006), and further descriptions of new species are immanent. This development has several, mutually not exclusive, reasons: i) discovery and characterization of new species, ii) resurrection of synonyms, and iii) the application of new species concepts. i) Since the beginning of the new millenium, 15 new lemur species have been described. Most of them were formerly lumped with closely resembling species and/or not recognized as distinct species (Avahi spp., Cheirogaleus spp., Lepilemur spp. Figure 5), Microcebus spp., Mirza zaza). ii) Accompanying such research efforts, nine old names have been resurrected from synonymy based on new information from the field and museum work (e.g. Cheirogaleus spp., Microcebus spp.), including two subspecies of the diurnal Varecia variegata (V. v. editorum and V. FIGURE 1. Comparative composition of Madagascar’s mammal fauna. Only in Madagascar are (non-human) primates the dominant order in number of genera. Based on Nowak (1999). MADAGASCAR CONSERVATION & DEVELOPMENT VOLUME 1 | ISSUE 1 — DECEMBER 2006 PAGE 6 v. subcincta). iii) Most influential was the application of a different species concept, the Phylogenetic Species Concept from Cracraft (1983). This led to the recognition of many former subspecies as species (for a detailed review see Thalmann, in press). PARTICULARITIES IN LEMURS Lemurs are not only endemic to Madagascar they also show interesting characteristics which are very particular amongst primates and even among mammals. This makes lemurs scientifically especially interesting for comparative studies with other primates in other regions. Unfortunately, only the smaller lemurs survived into our days, but once the lemur radiation covered a body mass range from 30 g (Microcebus berthae) to 150-200 kg (Archaeoindris). With 30 g Microcebus berthae, Madame Berthe’s mouse lemur is the smallest primate world wide. Some of the smaller lemurs belonging to the family Cheirogaleidae are able to reduce their metabolism and enter torpor or hibernation. Cheirogaleus medius, the fat-tailed dwarf lemur for example, spends several months during the austral winter to overcome the dry period in the dry portions of Madagascar where it occurs. Most of today’s surviving lemur species are nocturnal, in line with their usually small body size. In general, nocturnal primates are smaller than diurnal primates (Martin 1990). However, some diurnal species remain such as the Indri, Propithecus and Varecia. A third activity pattern cathemerality is present in many species of the genus Eulemur (e.g., Eulemur mongoz). These lemurs have activity peaks distributed over the entire daily 24 hr cycle, modified according to season (Curtis et al. 2006). Particularly interesting is the social organization of some lemurs. On average, they live in smaller groups than monkeys. In many species, females are dominant over males, which is unusual among primates. Also, an unusually high portion of the surviving lemurs live in pairs with their offspring. Indeed, based on investigations of nocturnal lemurs it has been shown that the ancestral social organization in primates was not a kind of harem. It was most likely either a dispersed multifemale/ multimale organization or they were organized in dispersed pairs (Müller and Thalmann 2000). Lemurs are usually seasonal breeders with seasonal birthpeaks. Offspring are carried from birth by their mothers in many species with singletons. Other species – mostly nocturnal smaller lemurs – have litter sizes of up to 4 and build nests for their offsprings. The nocturnal sportive lemurs usually cache their single offsprings while adults are foraging. The diurnal Varecia is an exception among diurnal lemurs and cathemeral lemurs because they usually have more than one offspring and leave them in nests until they can follow their mother. Lemurs cover a wide range of dietary regimes from primarily folivores to frugivores and omnivores. Some are highly special���� ����� ������ ���� ����� ������ �������� �������������������� ������ � �� � � � �� �� �� � � � � � �� �� � �� � � ��������������������� ����