Lemurs,Madagascar

• Lemurs   are a clade of strepsirrhine primates endemic to the island of Madagascar. The word "lemur" derives from the word lemures (ghosts or spirits) from Roman mythology and was first used to describe a slender loris due to its nocturnal habits and slow pace, but was later applied to the primates on Madagascar. HP Envy 14 Series CPU FANAlthough lemurs often are confused with ancestral primates, the anthropoid primates (monkeys, apes, and humans) did not evolve from them; instead, lemurs merely share morphological and behavioral traits with basal primates. Lemurs arrived in Madagascar around 62 to 65 mya by rafting on mats of vegetation at a time when ocean currents favored oceanic dispersal to the island. HP Envy 15 Series CPU FANSince that time, lemurs have evolved to cope with an extremely seasonal environment and their adaptations give them a level of diversity that rivals that of all other primate groups. Until shortly after humans arrived on the island around 2,000 years ago, there were lemurs as large as a male gorilla. Today, there are nearly 100 species of lemurs, and most of those species have been discovered or promoted to full species status since the 1990s; HP Envy 17 Series CPU FAN however, lemur taxonomic classification is controversial and depends on which species concept is used. Even the higher-level taxonomy is disputed, with some experts preferring to place most lemurs within the infraorder Lemuriformes, while others prefer Lemuriformes to contain all living strepsirrhines, placing all lemurs in superfamily Lemuroidea and all lorises and galagos in superfamily Lorisoidea. DELL XPS M1710 CPU FAN Ranging in size from 30 g (1.1 oz) to 9 kg (20 lb), lemurs share many common, basal primate traits, such as divergentdigits on their hands and feet and nails instead of claws (in most species). However, their brain-to-body size ratio is smaller than that of anthropoid primates, and among many other traits they share with other strepsirrhine primates, they have a "wet nose" (rhinarium). Lemurs are generally the most social of the strepsirrhine primates and communicate more with scents and vocalizations than with visual signals. HP 052907A CPU FAN Many lemur adaptations are in response to Madagascar's highly seasonal environment. Lemurs have relatively low basal metabolic rates and may exhibit seasonal breeding, dormancy (such as hibernation or torpor), or female social dominance. Most eat a wide variety of fruits and leaves, while some are specialists. Although many share similar diets, different species of lemur share the same forests by differentiating niches. HP 13.V1.B3403.GN CPU FAN Lemur research focused on taxonomy and specimen collection during the 18th and 19th centuries. Although field observations trickled in from early explorers, modern studies of lemur ecology and behavior did not begin in earnest until the 1950s and 1960s. Initially hindered by political instability and turmoil on Madagascar during the mid-1970s, field studies resumed in the 1980s and have greatly increased our understanding of these primates. HP 13.V1.BJ195.F.GN CPU FAN Research facilities like the Duke Lemur Center have provided research opportunities under more controlled settings. Lemurs are important for research because their mix of primitive characteristics and traits shared with anthropoid primates can yield insights on primate and human evolution. However, many lemur species are threatened with extinction due to habitat loss and hunting. Although local traditions generally help protect lemurs and their forests, illegal logging, HP 344872-001 CPU FAN widespread poverty, and political instability hinder and undermine conservation efforts. Because of these threats and their declining numbers, the International Union for Conservation of Nature (IUCN) considers lemurs to be the world's most endangered mammals, noting that—as of 2013—up to 90% of all lemur species face extinction within the next 20 to 25 years. HP 367795-001 CPU FAN Carl Linnaeus, the founder of modern binomial nomenclature, gave lemurs their name as early as 1758, when he used it in the 10th edition of Systema Naturae. He included three species under the genus Lemur: Lemur tardigradus (the red slender loris, now known as Loris tardigradus), Lemur catta (the ring-tailed lemur), and Lemur volans (the Philippine colugo, now known as Cynocephalus volans).^[2] HP 384622-001 CPU FAN Although the term "lemur" was first intended for slender lorises, it was soon limited to the endemic Malagasy primates, which have been known as "lemurs" ever since.^[3] The name derives from the Latin term lemures,^[4] which refers to specters or ghosts that were exorcised during the Lemuria festival of ancient Rome.^[5]According to Linnaeus' own explanation, the name was selected because of the nocturnal activity and slow movements of the slender loris.^[6] HP 3MLX6TATPH0 CPU FAN Being familiar with the works of Virgil and Ovid and seeing an analogy that fit with his naming scheme, Linnaeus adapted the term "lemur" for these nocturnal primates.^[7] However, it has been commonly and falsely assumed that Linnaeus was referring to the ghost-like appearance, reflective eyes, and ghostly cries of lemurs.^[6] It has also been speculated that Linnaeus may also have known that the some Malagasy people have held legends that lemurs are the souls of their ancestors,^[8] HP 3MLX8TATP20 CPU FAN but this is unlikely given that the name was selected for slender lorises from India. Lemurs are prosimian primates belonging to the suborder Strepsirrhini. Like other strepsirrhine primates, such as lorises, pottos, and galagos, they share ancestral (or plesiomorphic) traits with early primates. In this regard, lemurs are popularly confused with ancestral primates; however, lemurs did not give rise to monkeys and apes (simians). HP 3MLX8TATP40 CPU FAN Instead, they evolved independently in isolation on Madagascar.^[9] All modern strepsirrhines including lemurs are traditionally thought to have evolved from primitive primates known as adapiforms during the Eocene (56 to 34 mya) or Paleocene (65 to 56 mya).^[9][10][11]Adapiforms, however, lack a specialized arrangement of teeth, known as a toothcomb, which nearly all living strepsirrhines possess.^[ HP 3MLX9TATP70 CPU FAN A more recenthypothesis is that lemurs descended from lorisiform (loris-like) primates. This is supported by comparative studies of the cytochrome b gene and the presence of the strepsirrhine toothcomb in both groups.^[14][15] Instead of being the direct ancestors of lemurs, the adapiforms may have given rise to both the lemurs and lorisiforms, a split that would be supported by molecular phylogenetic studies.^[14] HP 407862-001 CPU FAN The later split between lemurs and lorises is thought to have occurred approximately 62 to 65 mya according to molecular studies,^[16] although other genetic tests and the fossil record in Africa suggest more conservative estimates of 50 to 55 mya for this divergence. Once part of the supercontinent Gondwana, the island of Madagascar has been isolated since it broke away from eastern Africa(~160 mya), HP 414226-001 CPU FAN Antarctica (~80–130 mya), and India (~80–90 mya).^[18][19] Since ancestral lemurs are thought to have originated in Africa around 62 to 65 mya, they would have had to have crossed the Mozambique Channel, a deep channel between Africa and Madagascar with a minimum width of about 560 km (350 mi).^[14] In 1915, paleontologist William Diller Matthew noted that the mammalian biodiversity on Madagascar (including lemurs) can only be accounted for by random rafting events, HP 418409-001 CPU FAN where very small populations rafted from nearby Africa on tangled mats of vegetation, which get flushed out to sea from major rivers.^[20] This form of biological dispersal can occur randomly over millions of years.^[14][21] In the 1940s, American paleontologist George Gaylord Simpson coined the term "sweepstakes hypothesis" for such random events.^[22] HP 431312-001 CPU FAN Rafting has since been the most accepted explanation for the lemur colonization of Madagascar,^[23][24] but until recently this trip was thought to be very unlikely because strong ocean currents flow away from the island.^[25] In January 2010, a report demonstrated that around 60 mya both Madagascar and Africa were 1,650 km (1,030 mi) south of their present-day positions, placing them in a different ocean gyre, producing currents that ran counter to what they are today. HP 434678-001 CPU FAN The ocean currents were shown to be even stronger than today, which would have pushed a raft along faster, shortening the trip to 30 days or less—short enough for a small mammal to survive easily. As the continental plates drifted northward, the currents gradually changed, and by 20 mya the window for oceanic dispersal had closed, effectively isolating the lemurs and the rest of the terrestrial Malagasy fauna from mainland Africa.^[25] HP 441137-001 CPU FAN Isolated on Madagascar with only a limited number of mammalian competitors, the lemurs did not have to compete with other evolving arboreal mammalian groups, such as squirrels.^[26] They were also spared from having to compete with monkeys, which evolved later. The intelligence, aggression, and deceptiveness of monkeys gave them an advantage over other primates in exploiting the environment. HP 448016-001 CPU FAN Lemurs have adapted to fill many open ecological niches since making their way to Madagascar.^[13][26] Their diversity in both behavior and morphology (outward appearance) rivals that of the monkeys and apes found elsewhere in the world.^[4] Ranging in size from the 30 g (1.1 oz) Madame Berthe's mouse lemur, the world's smallest primate,^[27] to the recently extinct 160–200 kg (350–440 lb) Archaeoindris fontoynonti,^[28] HP 450933-001 CPU FAN lemurs evolved diverse forms of locomotion, varying levels of social complexity, and unique adaptations to the local climate.^[13][29] Lemurs lack any shared traits that make them stand out from all other primates.^[30] Different types of lemurs have evolved unique combinations of unusual traits to cope with Madagascar's harsh, seasonal climate. These traits can include seasonal fat storage,hypometabolism (including torpor and hibernation), small group sizes, low encephalization (relative brain size), cathemerality(activity both day and night), and strict breeding seasons.^[10][29HP 456605-001 CPU FAN ^] Extreme resource limitations and seasonal breeding are also thought to have given rise to three other relatively common lemur traits: female social dominance, sexual monomorphism, and male–male competition for mates involving low levels of agonism, such as sperm competition.^[31] Before the arrival of humans roughly 1500 to 2000 years ago, lemurs were found all across the island.^[26] HP 480481-001 CPU FAN However, early settlers quickly converted the forests to rice paddies and grassland through slash-and-burn agriculture (known locally as tavy), restricting lemurs to approximately 10% of the island's area, ~60,000 km² (23,000 sq mi).^[32] Today, the diversity and complexity of lemur communities increases with floral diversity and precipitation and is highest in the rainforests of the east coast, where precipitation and floral diversity are also at their highest.^[11] HP 486799-001 CPU FAN Despite their adaptations for weathering extreme adversity, habitat destruction and hunting have resulted in lemur populations declining sharply, and their diversity has diminished, with the recent extinction of at least 17 species in eight genera,^[26][28][33] known collectively as the subfossil lemurs. Most of the approximately 100 species and subspecies of lemur are either threatened or endangered. Unless trends change, extinctions are likely to continue.^[34] HP 486844-001 CPU FAN Until recently, giant lemurs existed on Madagascar. Now represented only by recent or subfossil remains, they were modern forms that were once part of the rich lemur diversity that has evolved in isolation. Some of their adaptations were unlike those seen in their living relatives.^[26] All 17 extinct lemurs were larger than the extant (living) forms, some weighing as much as 200 kg (440 lb),^[4] and are thought to have been active during the day.^[35] HP 489126-001 CPU FAN Not only were they unlike the living lemurs in both size and appearance, they also filled ecological niches that either no longer exist or are now left unoccupied.^[26] Large parts of Madagascar, which are now devoid of forests and lemurs, once hosted diverse primate communities that included more than 20 lemur species covering the full range of lemur sizes. From a taxonomic standpoint, the term "lemur" originally referred to the genus Lemur, which currently contains only the ring-tailed lemur. HP 493001-001 CPU FAN The term is now used in the colloquial sense in reference to all Malagasy primates.^[39] Lemur taxonomy is controversial, and not all experts agree, particularly with the recent increase in the number of recognized species.^[30][40][41] According to Russell Mittermeier, the president of Conservation International (CI), taxonomist Colin Groves, and others, there are nearly 100 recognized species or subspecies of extant (or living) lemur, divided into five families and 15 genera.^[42] HP 495079-001 CPU FAN Because genetic data indicates that the recently extinct subfossil lemurs were closely related to living lemurs,^[43] an additional three families, eight genera, and 17 species can be included in the total.^[28][33] In contrast, other experts have labeled this as taxonomic inflation,^[41] instead preferring a total closer to 50 species.^[30] The classification of lemurs within the suborder Strepsirrhini is equally controversial, although the most experts agree on the same phylogenetic tree. HP 517749-001 CPU FAN In one taxonomy, infraorder Lemuriformes contains all living strepsirrhines in two superfamilies, Lemuroidea for all lemurs and Lorisoidea for the lorisoids (lorisids and galagos).^[17][44] Alternatively, the lorisoids are sometimes placed in their own infraorder, Lorisiformes, separate from the lemurs.^[45] In another taxonomy published by Colin Groves, the aye-ayewas placed in its own infraorder, Chiromyiformes, while the rest of the lemurs were placed in Lemuriformes and the lorisoids in Lorisiformes.^[46] HP 532141-001 CPU FAN Although it is generally agreed that the aye-aye is the most basal member of the lemur clade, the relationship between the other four families is less clear since they diverged during a narrow 10 to 12 million-year window between the Late Eocene (42 mya) and into the Oligocene (30 mya).^[16][23] Although all studies place Cheirogaleidae and Lepilemuridae as a sister clade to Indriidae and Lemuridae, some suggest that Cheirogaleidae and Lepilemuridae diverged first,^[ HP 532613-001 CPU FAN while others suggest that Indriidae and Lemuridae were the first to branch off. Lemur taxonomy has changed significantly since the first taxonomic classification of lemurs by Carl Linnaeus in 1758. One of the greatest challenges has been the classification of the aye-aye, which has been a topic of debate up until very recently.^[4] Until Richard Owen published a definitive anatomical study in 1866, early naturalists were uncertain whether the aye-aye (genus Daubentonia) was a primate, rodent, or marsupial.^[ HP 532614-001 CPU FAN However, the placement of the aye-aye within the order Primates remained problematic until very recently. Based on its anatomy, researchers have found support for classifying the genus Daubentonia as a specialized indriid, a sister group to all strepsirrhines, and as an indeterminate taxon within the order Primates.^[15] Molecular tests have now shown Daubentoniidae is basal to all Lemuriformes,^[ HP 532617-001 CPU FAN and in 2008, Russell Mittermeier, Colin Groves, and others ignored addressing higher-level taxonomy by defining lemurs as monophyletic and containing five living families, including Daubentoniidae.^[42]