Scott C. Pedersen

Phylogenetics and Phylogeography of the Artibeus jamaicensis Complex Based on Cytochrome-b DNA Sequences

Abstract The phylogenetics and phylogeography of the Jamaican fruit-eating bat (Artibeus jamaicensis) were examined based on analysis of DNA sequence variation in the mitochondrial cytochrome-b gene for 176 individuals representing all 13 subspecies of A. jamaicensis (sensu Simmons 2005). Results document that A. jamaicensis (sensu Simmons 2005) comprises 3 monophyletic assemblages that are separated phylogenetically by the presence of A. obscurus, A. lituratus, and A. amplus. According to the mitochondrial DNA sequence variation, A. jamaicensis, A. schwartzi, and A. planirostris are appropriate species-level names for these lineages. Haplotypes identifiable as A. jamaicensis were absent east of the Andes Mountains in South America; haplotypes of A. schwartzi were documented throughout the Lesser Antilles and from northern Venezuela, and haplotypes of A. planirostris were identified east of the Andes Mountains in South America, north of the Orinoco River in Venezuela, and from the southern Lesser Antilles. Haplotypes of Artibeus jamaicensis, A. schwartzi, and A. planirostris were identified sympatrically on Carriacou, a small island in the southern Lesser Antilles that is ecologically monotypic. The magnitude of genetic divergence separating A. jamaicensis, A. planirostris, and A. schwartzi essentially equals the magnitude of genetic divergence distinguishing A. lituratus, A. obscurus, and A. jamaicensis. Studies of the nuclear genome will be required to understand the biological implications of these patterns in the mitochondrial genome.

Cephalometric correlates of echolocation in the chiroptera: II. Fetal development

Cephalometry was used to detect patterns of cranial growth in fetal bats that were stained differentially for bone and cartilage. Three developmental features distinguish embryos of taxa that echolocate nasally from embryos of taxa that echolocate orally: (1) the basicranium is retained ventral to the cervical axis, (2) the rostrum is retained below the basicranial axis, and (3) the lateral semicircular canals are rotated caudally. Together, the first two actions align the fetal nasal cavity with what will be the long axis of the adult body in flight. The third action aligns the lateral semicircular canals with the horizontal. In contrast, skulls of oral‐emitting taxa are constructed such that the oral cavity is aligned with the long axis of the body in flight. The evolution of head posture and skull form in microchiropteran bats has been constrained by the demands of vocalization, i.e., ultrasonic echolocation. Accordingly, the ontogeny of the microchiropteran skull has been canalized along two distinct developmental paths—oral‐emitting and nasal‐emitting Baupläne.

Calcium as a limiting resource to insectivorous bats: can water holes provide a supplemental mineral source?

Data are presented on a bat assemblage captured among 10 water holes in Colorado over 5 years. The assemblage consists of Myotis ciliolabrum, M. evotis, M. lucifugus, M. thysanodes, M. volans, Eptesicus fuscus, Lasiurus cinereus, Lasionycteris noctivagans and Corynorhinus townsendii .R esults show that reproductive females and juveniles are captured in higher frequencies at water holes containing higher water hardness and that water hardness correlates highly significantly with dissolved calcium content. Also presented are laboratory test data on the stomach volume of Eptesicus fuscus that provide a model for understanding the effect of dissolved calcium content in water as a significant resource. These data indicate that water holes provide supplemental sources of calcium for bats not provided by diet.

Mist netting bias, species accumulation curves, and the rediscovery of two bats on Montserrat (Lesser Antilles)

ABSTRACT Mist nets are commonly used to survey bat populations and to estimate bat biodiversity, but several studies have found that mist net capture data and methods are biased due to a number of factors, including size and placement of nets, and the frequency at which investigators check their nets. Despite the wealth of literature and anecdotal reports, few investigators have quantified the interactions of bats with mist nets directly. We employed night vision camcorders to monitor bat behavior when bats encountered a mist net and then utilized these data to reevaluate years of survey data collected on Montserrat, Lesser Antilles. We recorded 2,523 bat passes during 43.3 hours of videotaping in July 2005 and June 2006. Observations conducted on successive nights provide evidence of avoidance-learning behavior in bats. When a mist net was present, 5.4% of bats in the airspace came into contact with the net giving an overall capture rate of 3.2% (range 0–10.3%). Mist nets are not accurately sampling bats that utilize flyways on Montserrat and such fieldwork thereby generates potentially misleading data. Biodiversity assessments and conservation guidelines based on short-term mist net surveys alone are not sufficient or reliable in regards to bats. A pragmatic solution to reduce mist net bias is to repeatedly sample a target region, utilize a variety of netting sites, use variable net sets, and carefully analyze species accumulation curves.

Morphometric Analysis of the Chiropteran Skull with Regard to Mode of Echolocation

I compared simple morphometric data with cephalometric data on the angular arrangements of the facial and neural components of the skull of bats. The morphological dichotomy between oral and nasal emission of the echolocation pulse in the Microchiroptera is presumably under strong selective pressure to provide an acoustical horn for efficient emission of the echolocative call. Cephalometric and morphometric data compliment each other in the distinction between oral and nasal bauplane . However, fine taxonomic resolution provided by morphometric data is subject to the otherwise plastic functional matrix of the head conforming to the acoustical axis of the skull.

Bats of Nevis, Northern Lesser Antilles

Only one species of bat, Molossus molossus, previously has been documented as occurring on the northern Lesser Antillean island of Nevis. Field research and reviews of existing museum collections have provided documentation based on voucher specimens for an additional seven species occurring on the island — Noctilio leporinus, Brachyphylla cavernarum, Monophyllus plethodon, Ardops nichollsi, Artibeus jamaicensis, Natalus stramineus, and Tadarida brasiliensis. The biological diversity of the chiropteran fauna on Nevis is similar to that found on other islands in the northern Lesser Antilles. Ecologically, this is a simple chiropteran fauna, including one piscivore (N. leporinus), one omnivore (B. cavernarum), one pollenivore/nectivore (M. plethodon), two frugivores (A. nichollsi, A. jamaicensis), and three insectivorous species (N. stramineus, T. brasiliensis, M. molossus). Species-area and species-elevation analyses for the chiropteran fauna of the Greater and Lesser Antillean islands gave r 2 values of 0.74 and 0.33, respectively. In the species-area analysis the bat fauna of Nevis falls above the regression line and in the species-elevation analysis it falls almost on the line. The chiropteran fauna of Nevis lies outside the Lesser Antillean Faunal Core and would be best characterized as a generalized Lesser Antillean fauna that appears to be characteristic of the northern Lesser Antilles.

Ontogeny of bone strain: the zygomatic arch in pigs

SUMMARY At the time of weaning, infant animals have little experience with hard food, and thus their skulls are not likely to be epigenetically adapted for the loads imposed by mastication. We examined bone strain in the zygomatic arch of 4-week-old weanling piglets. Functional strains in piglets differed from those previously reported for older pigs in that the squamosal bone was not bent in the horizontal plane and the principal tensile strain on the zygomatic bone did not correspond to the direction of masseter muscle pull. Strain patterns were more variable in piglets than in older pigs. In older pigs, masticatory strains can be reproduced by stimulating the masseter muscles. When the piglet masseter was stimulated, strain patterns were more similar to those of older pigs, but shear strain magnitudes were the largest yet recorded from mammalian skull bones, up to 4000 μϵ. To put these findings in the context of skeletal adaptation, 45 dry skulls, including some animals from the strain study, were measured. Reduced major axis regressions indicated that the infant arch was rounder in cross section and straighter than that of older animals. With growth, the arch became dorsoventrally higher, while mediolateral thickness decreased in the squamosal bone. Overall, these changes should make strain more predictable, explaining the lower variability in older animals. Other factors likely to be important in causing unique strain regimes in piglets include (1) unfamiliarity with hard food, (2) greater importance of muscles other than the same-side masseter and (3) greater proximity of molariform teeth to the arch. Collectively, these data indicate that the skeleton is not pre-adapted for specific functional loads.

Bat Evolution, Ecology, and Conservation

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Activity Patterns and Roost Selection by Noctilio albiventris (Chiroptera: Noctilionidae) in Costa Rica

Using radiotracking and direct observation we documented activity patterns and roost selection of Noctilio albiventris at the Estacion Experimental Enrique Jimanez Nunez near Canas, Costa Rica. Bats with radiotransmitters showed little consistency in their use of foraging areas. Observations of captive and free-flying animals suggested that time away from the roosts represented foraging time. Individual bats showed considerable variation in both foraging time and numbers of foraging bouts per night, but total time away from the roost usually averaged 120 min/night. Bats with radiotransmitters roosted in hollow trees and, although most used the same roosts repeatedly, some changed roosts during the study period.

Lancet Dynamics in Greater Horseshoe Bats, Rhinolophus ferrumequinum

Echolocating greater horseshoe bats (Rhinolophus ferrumequinum) emit their biosonar pulses nasally, through nostrils surrounded by fleshy appendages (‘noseleaves’) that diffract the outgoing ultrasonic waves. Movements of one noseleaf part, the lancet, were measured in live bats using two synchronized high speed video cameras with 3D stereo reconstruction, and synchronized with pulse emissions recorded by an ultrasonic microphone. During individual broadcasts, the lancet briefly flicks forward (flexion) and is then restored to its original position. This forward motion lasts tens of milliseconds and increases the curvature of the affected noseleaf surfaces. Approximately 90% of the maximum displacements occurred within the duration of individual pulses, with 70% occurring towards the end. Similar lancet motions were not observed between individual pulses in a sequence of broadcasts. Velocities of the lancet motion were too small to induce Doppler shifts of a biologically-meaningful magnitude, but the maximum displacements were significant in comparison with the overall size of the lancet and the ultrasonic wavelengths. Three finite element models were made from micro-CT scans of the noseleaf post mortem to investigate the acoustic effects of lancet displacement. The broadcast beam shapes were found to be altered substantially by the observed small lancet movements. These findings demonstrate that—in addition to the previously described motions of the anterior leaf and the pinna—horseshoe bat biosonar has a third degree of freedom for fast changes that can happen on the time scale of the emitted pulses or the returning echoes and could provide a dynamic mechanism for the encoding of sensory information.