Colugo

Abstract: The three living monophyletic divisions of Class Mammalia are the Prototheria (monotremes), Metatheria (marsupials), and Eutheria ('placental' mammals). Determining the sister relationships among these three groups is the most fundamental question in mammalian evolution. Phylogenetic comparison of these mammals by either anatomy or mitochondrial DNA has resulted in two conflicting hypotheses, Theria and Marsupionta, and has fueled a "genes versus morphology" controversy. We have cloned and analyzed a large nuclear gene, the mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R), from representatives of all three mammalian groups, including platypus, echidna, opossum, wallaby, hedgehog, mouse, rat, rabbit, cow, pig, bat, tree shrew, colugo, ringtail lemur, and human. Statistical analysis of this nuclear gene unambiguously supports the morphology-based Theria hypothesis that excludes monotremes from a clade of marsupials and eutherians. The M6P/IGF2R was also able to resolve the finer structure of the eutherian mammalian family tree. In particular, our analyses support sister group relationships between lagomorphs and rodents, and between the primates and Dermoptera. Statistical support for the grouping of the hedgehog with Feruungulata and Chiroptera was also strong.

Abstract: Arboreal animals negotiate a highly three-dimensional world that is discontinuous on many spatial scales. As the scale of substrate discontinuity increases, many arboreal animals rely on leaping or gliding locomotion between distant supports. In order to successfully move through their habitat, gliding animals must actively modulate both propulsive and aerodynamic forces. Here we examined the take-off and landing kinetics of a free-ranging gliding mammal, the Malayan colugo (Galeopterus variegatus) using a custom-designed three-dimensional accelerometry system. We found that colugos increase the propulsive impulse to affect longer glides. However, we also found that landing forces are negatively associated with glide distance. Landing forces decrease rapidly as glide distance increases from the shortest glides, then level off, suggesting that the ability to reorient the aerodynamic forces prior to landing is an important mechanism to reduce velocity and thus landing forces. This ability to substantially alter the aerodynamic forces acting on the patagial wing in order to reorient the body is a key to the transition between leaping and gliding and allows gliding mammals to travel long distances between trees with reduced risk of injury. Longer glides may increase the access to distributed resources and reduce the exposure to predators in the canopy or on the forest floor.

Abstract: Although a general agreement on the major groups of eutherian orders and their phylogenetic affiliations is emerging, the evolutionary affiliations among the members constituting these groups are still subject to debate. A prominent example is the recently published molecular evidence that challenges the long assumed monophyly of primates, displaying the colugo or flying lemur (Cynocephalus, Dermoptera) as a sister to anthropoid primates (Arnason et al. 2002 ) and positioning them after the prosimian primates (tarsiers and strepsirhines) split off. The phylogenetic analysis of the complete mitochondrial (mt) genome sequence of Cynocephalus variegatus presented in this study first appears to corroborate interpretations of primates as a paraphyletic group. However, more detailed analyses disclosed that mt nucleotide composition and consequently amino acid (AA) composition varied considerably among the species analyzed. This led us to assume that the flying lemur may be incorrectly grouped with anthropoids on the basis of similar mt nucleotide and AA compositions, rather than reflecting the true evolutionary relationship. To reanalyze the flying lemur's evolutionary association with other eutherian orders from a completely different molecular perspective, a molecular cladistic approach was applied. To this end, we determined the presence/absence pattern of transposable elements that provide a nearly homoplasy-free and copious source of molecular evolutionary markers, with well-defined character polarity. We could identify transposable elements, both on a multilocus and single-locus level, being present in all extant primate infraorders but absent in the flying lemur, thus clearly supporting the monophyly of primates by retropositional evidence.

Abstract: ?Two conflicting hypotheses concern the origin of flying mammals. The traditional hypothesis states that the two major groups of bats, the microchiropterans and the megachiropterans, are sister groups that constitute the taxon Chiroptera. In contrast, the diphyly hypothesis suggests that megachiropterans are more closely related to primates than to microchiropterans. Different suites of morphological characters provide support for each of these hypotheses, and previous molecular studies have not provided a clear resolution of the problem. We analyzed a region of the mitochondrial 12S ribosomal RNA gene from ll species of mammals, including 2 species of megachiropterans, 2 species of microchiropterans, a primate, a colugo (Dermoptera), a tree shrew (Scandentia), and 4 outgroups, to test the diphyly hypothesis. A phylogenetic analysis of 257 base pairs resulted in two shortest unrooted trees that significantly support the monophyly of the bats and also suggest that the colugo is more closely related to primates than to the bats: (((Primates, Dermoptera) Scandentia) (Microchiroptera, Megachiroptera)). The topology sup? porting the diphyly hypothesis is 10 steps longer than the most-parsimonious unrooted tree. Although the traditional hypothesis is supported with respect to bat monophyly, the rDNA data support the nontraditional grouping of colugo and primates (a hypothesis also supported by neurological data). [Bat monophyly, phylogenetic confidence, Chiroptera, Archonta.] All mammals capable of true flight tra? ditionally have been recognized as a monophyletic group, Chiroptera. The two major lineages of bats have been united based on several unique musculoskeletal specializations associated with the pres? ence of wings (Baker et al., 1991b). Re? cently, doubt has been raised over the support for a bat dade. Are the large fruiteating bats of the Old World (Megachiroptera) the closest living relatives of the smaller predominantly insectivorous cos? mopolitan bats known as microchiropterans? The monophyly of Chiroptera was questioned first by Smith (1977) and Smith and Madkour (1980). They concluded that derived features of the penis, neurosensory system (size of neocortex), and limb joints suggest a diphyletic origin for bats, or that mammals evolved flight twice. The diphyly hypothesis also has been support? ed by Pettigrew (1986) based upon several features related to the patterns of connec? tion between the retina and midbrain (su? perior colliculus) that are shared in pri? mates and megachiropterans. Predictably, these findings have sparked a controversy 1 Present address; Department of Biology, Texas Wesleyan University, Fort Worth, Texas 76105, USA. over bat relationships. The evidence sup? porting opposing sides of the argument was recently summarized by Pettigrew (1991a, 1991b), Baker et al. (1991b), and Simmons et al. (1991). The disagreement among existing mor? phological studies (Simpson, 1945; Smith, 1977; Smith and Madkour, 1980; Novacek, 1982; Pettigrew, 1986; Shoshani, 1986; Wible and Novacek, 1988; Pettigrew et al., 1989; Thewissen and Babcock, 1991) makes this particular problem an excellent can? didate for molecular analysis. Which suite of characters are truly the result of com? mon ancestry and which are convergent? The differences between the megabats and microbats are widely known (Pettigrew et al., 1989), but synapomorphies for Chirop? tera have been much more elusive. The bats are generally regarded as part of the superorder Archonta (Novacek, 1989), along with Primates, Dermoptera (colugos or flying lemurs), and Scandentia (tree shrews). Bats and colugos traditionally have been recognized as sister taxa (Fig. la), whereas Pettigrew et al. (1989) hypothe? sized a sister-group relationship between one of the groups of bats (megachiropterans) and primates (Fig. lb). There is very little consensus regarding the relation-