Flight style in bats as predicted from wing morphometry: the effects of specimen preservation

An as yet unconsidered potential error in studies that predict flight style from morphological measurements of bats is the effect of the specimen type employed. On the basis of the finding that morphological measurements taken from fluid-preserved bat specimens may not yield values equivalent to those taken from the live animal, we compared the values of several variables (lifting surface area, wingspan, mass, aspect ratio, wing loading and minimum power speed) for live and fluid-preserved little brown bats ( Myotis lucifugus ) with the accepted standards for this species given by Norberg & Rayner (1987). Significant differences were detected for lifting surface area, wingspan, mass, aspect ratio and wing loading values taken from live bats and their respective values reported by Norberg & Rayner. Differences between preserved bats and Norberg & Rayner's numbers were limited to lifting surface area and wingspan (extended wing positions only), aspect ratio (all wing positions), and mass (both 70% ethanol- and 45% isopropyl alcohol-preserved specimens). Thus, Norberg & Rayner's values correspond most closely to values obtained from preserved museum specimens, a fact reflecting the source of their data in this instance. This and other limitations involved in attempting to predict the flight style of bats from a few morphological characters are discussed.     

The impact of species concept on biodiversity studies

Species are defined using a variety of different operational techniques. While discussion of the various methodologies has previously been restricted mostly to taxonomists, the demarcation of species is also crucial for conservation biology. Unfortunately, different methods of diagnosing species can arrive at different entities. Most prominently, it is widely thought that use of a phylogenetic species concept may lead to recognition of a far greater number of much less inclusive units. As a result, studies of the same group of organisms can produce not only different species identities but also different species range and number of individuals. To assess the impact of different definitions on conservation issues, we collected instances from the literature where a group of organisms was categorized both under phylogenetic and nonphylogenetic concepts. Our results show a marked difference, with surveys based on a phylogenetic species concept showing more species (48%) and an associated decrease in population size and range. We discuss the serious consequences of this trend for conservation, including an apparent change in the number of endangered species, potential political fallout, and the difficulty of deciding what should be conserved.     

Assessment of the accuracy of matrix representation with parsimony analysis supertree construction

Despite the growing popularity of supertree construction for combining phylogenetic information to produce more inclusive phylogenies, large-scale performance testing of this method has not been done. Through simulation, we tested the accuracy of the most widely used supertree method, matrix representation with parsimony analysis (MRP), with respect to a (maximum parsimony) total evidence solution and a known model tree. When source trees overlap completely, MRP provided a reasonable approximation of the total evidence tree; agreement was usually > 85%. Performance improved slightly when using smaller, more numerous, or more congruent source trees, and especially when elements were weighted in proportion to the bootstrap frequencies of the nodes they represented on each source tree ("weighted MRP"). Although total evidence always estimated the model tree slightly better than nonweighted MRP methods, weighted MRP in turn usually out-performed total evidence slightly. When source studies were even moderately nonoverlapping (i.e., sharing only three-quarters of the taxa), the high proportion of missing data caused a loss in resolution that severely degraded the performance for all methods, including total evidence. In such cases, even combining more trees, which had positive effects elsewhere, did not improve accuracy. Instead, "seeding" the supertree or total evidence analyses with a single largely complete study improved performance substantially. This finding could be an important strategy for any studies that seek to combine phylogenetic information. Overall, our results suggest that MRP supertree construction provides a reasonable approximation of a total evidence solution and that weighted MRP should be used whenever possible.     

A phylogenetic supertree of the bats (Mammalia: Chiroptera)

We present the first estimate of the phylogenetic relationships among all 916 extant and nine recently extinct species of bats Mammalia: Chiroptera), a group that accounts for almost one-quarter of extant mammalian diversity. This phylogeny was derived by combining 105 estimates of bat phylogenetic relationships published since 1970 using the supertree construction technique of Matrix Representation with Parsimony (MRP). Despite the explosive growth in the number of phylogenetic studies of bats since 1990, phylogenetic relationships in the order have been studied non-randomly. For example, over one-third of all bat systematic studies to date have locused on relationships within Phyllostomidae, whereas relationships within clades such as Kerivoulinae and Murinae have never been studied using cladistic methods. Resolution in the supertree similarly differs among clades: overall resolution is poor (46.4%, of a fully bifurcating solution) but reaches 100% in some groups (e.g. relationships within Mormoopidae). The supertree analysis does not support a recent proposal that Microchiroptera is paraphyletic with respect to Megachiroptera, as the majority of source topologies support microbat monophyly. Although it is not a substitute for comprehensive phylogenetic analyses of primary molecular and morphological data, the bat supertree provides a useful tool for future phylogenetic comparative and macroevolutionary studies. Additionally, it identifies clades that have been little studied, highlights groups within which relationships are controversial, and like all phylogenetic studies, provides preliminary hypotheses that can form starting points for future phylogenetic studies of bats.     

Novel versus unsupported clades: assessing the qualitative support for clades in MRP supertrees

Matrix representation with parsimony (MRP) supertree construction has been criticized because the supertree may specify clades that are contradicted by every source tree contributing to it. Such unsupported clades may also occur using other supertree methods; however, their incidence is largely unknown. In this study, I investigated the frequency of unsupported clades in both simulated and empirical MRP supertrees. Here, I propose a new index, QS, to quantify the qualitative support for a supertree and its clades among the set of source trees. Results show that unsupported clades are very rare in MRP supertrees, occurring most often when there are few source trees that all possess the same set of taxa. However, even under these conditions the frequency of unsupported clades was <0.2%. Unsupported clades were absent from both the Carnivora and Lagomorpha supertrees, reflecting the use of large numbers of source trees for both. The proposed QS indices are correlated broadly with another measure of quantitative clade support (bootstrap frequencies, as derived from resampling of the MRP matrix) but appear to be more sensitive. More importantly, they sample at the level of the source trees and thus, unlike the bootstrap, are suitable for summarizing the support of MRP supertree clades.     

A complete phylogeny of the whales, dolphins and even-toed hoofed mammals (Cetartiodactyla)

Despite the biological and economic importance of the Cetartiodactyla, the phylogeny of this clade remains controversial. Using the supertree approach of matrix representation with parsimony, we present the first phylogeny to include all 290 extant species of the Cetacea (whales and dolphins) and Artiodactyla (even-toed hoofed mammals). At the family-level, the supertree is fully resolved. For example, the relationships among the Ruminantia appear as (((Cervidae, Moschidae) Bovidae) (Giraffidae, Antilocapridae) Tragulidae). However, due to either lack of phylogenetic study or contradictory information, polytomies occur within the clades Sus, Muntiacus, Cervus, Delphinidae, Ziphiidae and Bovidae. Complete species-level phylogenies are necessary for both illustrating and analysing biological, geographical and ecological patterns in an evolutionary framework. The present species-level tree of the Cetartiodactyla provides the first opportunity to examine comparative hypotheses across entirely aquatic and terrestrial species within a single mammalian order.     

Palaeoecological significance of Barremian ammonite assemblages and facies variations from Southwest Mexico

Analyses of ammonite shell forms of two Barremian stratigraphic sections from Southwest Mexico consist of two well-defined morphotypes: (1) Small uncoiled, mostly leptoceratoid ancyloconic shells of the families Ancyloceratidae and Hamulinidae, and (2) middle-sized involute to moderately evolute oxycone to discocone shells of the family Pulchelliidae. Index taxa allow the recognition of standard ammonite biozones for the Barremian, which permit the relative dating of different processes that occurred through the water column in the environment of deposition. The vertical distribution of ammonite morphotypes and facies suggests changes of the palaeoceanographic and sedimentological conditions that prevailed in the area during Barremian time. Petrologic data, analyses of the organic carbon and carbonate contents of the rocks support the idea that oxygen-deficient bottom waters existed within a shallow marine, tectonically active area with little carbonate deposition during the early early Barremian (upper part of the Taveraidiscus hugii Zone through the base of the Nicklesia pulchella Zone). These conditions in the basin caused a proliferation of middle-water depth ammonites of Morphotype 1 but prevented the abundance of nektobenthic forms of Morphotype 2. Oxic conditions on a more calcareous and open normal marine environment seem to have been reestablished progressively during a transgressive episode from late early-early late Barremian (upper part of the Nicklesia pulchella Zone through the Gerhardtia sartousiana Zone). This environmental setting supported more facies dependent nektobenthic ammonites of Morphotype 2 to flourish within the basin.     

Immediate and heritable costs of desiccation on the life history of the bdelloid rotifer <Emphasis Type="Italic">Philodina roseola</Emphasis>

The long-term persistence of the ‘ancient asexual’ bdelloid rotifers, a clade of small aquatic invertebrates, is often tied to their ability to enter anhydrobiosis. This ability has both clear benefits (e.g. survival of desiccating conditions), but offers considerable costs (e.g. subsequent repair of the genome as well as physiological and metabolic costs to re-establish the phenotype). Despite these costs, several studies show that the time spent dry is effectively ignored with respect to life expectancy (the Sleeping Beauty hypothesis) and that reconstruction of the genome after a desiccation event might even be necessary to repair mistakes accumulated in it from obligate parthenogenesis while the animals were active. We propose that this genomic repair might not derive exclusively because desiccation per se, but could also result from genetic exchange that appears to occur between individuals during this time. By comparing individuals of Philodina roseola Ehrenberg, 1832 desiccated in groups versus individually, we document costs to desiccation in the isolated treatment group that impact negatively on lifespan and reproduction. In addition, comparing both groups with continuously active individuals reveals no strong evidence for the Sleeping Beauty hypothesis in this species nor any decline in fitness over a six-month period for the latter group. Finally, many treatment effects are at least partly heritable and were found in the untreated F1 generations. In particular, individuals desiccated in groups and their offspring could both reproduce faster than the offspring of continuously active individuals. Thus, our results offer additional support for the hypothesis of genetic exchange occurring during desiccation events in P. roseola and highlight the importance of considering this factor, and desiccation in general, in explaining bdelloid fitness. Moreover, our results provide additional context for understanding how the genetic information of bdelloids is ultimately shaped.