Cliff A. Lemen

Measuring Bite Force in Small Mammals with a Piezo-resistive Sensor

Abstract We tested the use of piezo-resistive force sensors to measure bite force in small mammals. These force sensors are thin (less than 1 mm) and can be used to measure forces up to 4,500 N. A battery-operated unit, ideal for field research, can be built easily and inexpensively. We tested this sensor in the laboratory and in the field on a variety of small mammals. Although our results indicate that the sensor is somewhat less accurate (coefficient of variation = 4%) than a conventional load cell, the small size and ease of use of the piezo-resistive detector is highly desirable. We also investigated the problem of performance and physiological condition of animals. We found the problem of lack of effort by test animals can enter a significant bias into estimates of maximal bite force.

THE GENUS: A MACROEVOLUTIONARY PROBLEM

Although much of the recent work on macroevolution has centered on the fossil record (Gould, 1980), a few studies have addressed this concept using the morphology of living species as a data base (Ricklefs, 1980; Lemen and Freeman, 1981). The neontological record does lack the element of time that allows a researcher to follow change through time, but this deficiency is counterbalanced by the fact that living species represent one perfect slice of time. Admittedly systematists have not been able to collect and classify all extant species, but tests using the neontological record in the better known groups such as birds and mammals will not suffer the problems of incomplete data sets or uncertain chronologies as badly as is probable with the paleontological record. One way to use neontological data is to study how species are arranged in morphological space. The evolutionary diversification of a clade can be seen as a tree that spreads with morphological change and branches with cladogenesis. In such a vision living species are one cross-sectional slice of the tree. The problem is to find what this cross section reveals about the structure of the tree. Perhaps the best way to start visualizing this approach is by considering that all clades ultimately trace their ancestry to a single species. Therefore, one can imagine a clade evolving from one species to many and filling morphological space through time in a certain way that is based on the number of species in the clade and the individual morphologies of the species. The specific morphologies of these species are not predictable because they are the products of the unique environment, history and stochastic processes that species face. However, if all clades share certain fundamental evolutionary processes, then some repeated patterns that depend on these shared processes might be expected in all clades. This paper centers on the macroevolutionary problem surrounding the concept of the vertebrate genus. We have been fascinated by the apparent tendency of members of a genus to have the same shape in contrast to the great differences in shape among genera at the family level. If this is true, genera would be considered shape conservative groups. Our initial view of this contrast in shape variation within and among genera leads us to question whether the same evolutionary processes that produce genera can simply be extended to produce families. To approach this question two things need to be done. First, the morphology of genera must be quantified to yield a more exact idea of how the morphological variation of a family is partitioned into genera. And second, evolutionary models need to be built that make different assumptions about how evolution proceeds. Our quantification of the morphology of genera will involve looking at size and shape variation at the familial and generic levels with multivariate methods. The evolutionary models will be used to make predictions of size and shape variation in families and genera under different evolutionary assumptions. As will be presented below, our models make clearly different predictions of how species will

Interference competition in a heteromyid community in the Great Basin of Nevada, USA

Removal experiments with three species of heteromyid rodents were performed during two summers in the Great Basin of Nevada, USA. These experiments were designed to determine the importance of interference competition in these species by quantifying the short-term responses to the removal of one or more of the species. Our results indicate that the removal of a large species (Dipodomys merriami) does have a positive effect on a smaller species with a similar diet (Perognathus longimembris). These results and others presented are consistent with a hypothesis of interference competition. However, while there is short-term increase in number of rodents in response to removals, the increase is not commensurate with the number of animals removed. We conclude that interference competition was present but weak in the two summers we manipulated this community.

The Problem of Low Agreement among Automated Identification Programs for Acoustical Surveys of Bats

Abstract. We compared 4 programs designed to identify species of bats from their echolocation calls (Bat Call ID, EchoClass, Kaleidoscope Pro, and SonoBat) using field data collected in Nebraska, USA (29,782 files). Although we did not know the true identity of these bats, we could still compare the pairwise agreement between software packages when identifying the same call sequences. If accuracy is high in these software packages, there should be high agreement in identification. Agreement in identification by species averaged approximately 40% and varied by software package, species, and data set. Our results are not consistent with the high accuracy often claimed by some software packages and may be a warning about the importance of understanding accuracy of acoustical identification in designing ecological experiments and interpreting results.

TESTING MACROEVOLUTIONARY HYPOTHESES WITH CLADISTIC ANALYSIS: EVIDENCE AGAINST RECTANGULAR EVOLUTION

The properties of cladistic data sets from small monophyletic groups (6–12 species) are investigated using computer simulations of macroevolution. Two evolutionary models are simulated: gradualism and the punctuated‐equilibrium hypothesis. Under the conditions of our simulations these two models of evolution make consistently different predictions about the distribution of autapomorphies among species. When strict stasis is enforced, the punctuated‐equilibrium hypothesis predicts that the most expected number of autapomorphies per species will be zero, no matter how many characters are used in the analysis. As the number of characters used in the analysis increases, the distribution of the number of autapomorphies per species becomes bimodal. Under gradualism, the distribution of autapomorphies remains unimodal under all conditions, but the number of species without autapomorphies can fall to zero. A survey of real cladograms of extant monophyletic groups from a wide range of taxa indicates that the predictions of the punctuated‐equilibrium hypothesis about autapomorphies do not hold. This constitutes strong evidence against the punctuated‐equilibrium hypothesis.

A test of macroevolutionary problems with neontological data

-Ricklefs (1980) suggested the use of neontological data to distinguish between puncuated equilibrium and gradualism as modes of evolution. This paper investigates his model and finds it contains oversimplifications that make any test difficult. We modify his model slightly and use it as a limited test of punctuated equilibrium by large morphological shifts at speciation. This test is applied to a data set of 110 species from two families of bats, the Emballonuridae and the Molossidae. We find no evidence of consistently large morphological shifts at the formation of subspecies, species or genera. Cliff A. Lemen. Department of Zoology, Field Museum of Natural History, Chicago, Illinois 60605. Present address: School of Life Sciences, Manter Hall, University of Nebraska, Lincoln, Nebraska 68588 Patricia W. Freeman. Department of Zoology, Field Museum of Natural History, Chicago, Illinois 60605. Present address: University of Nebraska State Museum, Nebraska Hall, Lincoln, Nebraska 68588 Accepted: May 4, 1981

Acoustic Detection Reveals Fine-Scale Distributions of Myotis lucifugus, Myotis septentrionalis, and Perimyotis subflavus in Eastern Nebraska

Abstract. Before white-nose syndrome arrives in Nebraska, it is important to document the preexposure distributions of cave bats in the state. We examined the distributions of Myotis lucifugus (little brown myotis), Myotis septentrionalis (northern long-eared myotis), and Perimyotis subflavus (tri-colored bat) in eastern Nebraska by setting acoustic detectors for a single night at 105 sites in wooded habitats during summers of 2012 and 2014. We compared 2 methods of determining presence at each site. Results of our analyses are fine-scale distributional maps for these bats and some range extensions from published records. Results for M. septentrionalis and P. subflavus are largely consistent with previous reports. Results for M. lucifugus vary depending on the method of determining presence; however, our preferred method creates a pattern consistent with the known vouchered distribution of this species. The differences between published distributions of these species and distributions based on acoustic detection from our study might result from a lack of extensive netting in many areas of eastern Nebraska, underrepresentation of P. subflavus from mist net surveys in Nebraska, and a recent westward range expansion of P. subflavus and M. septentrionalis in southern Nebraska.

Puncture-Resistance of Gloves for Handling Bats

Abstract We quantified protection given by a variety of gloves against bat bites by using steel indenters to simulate teeth and measuring forces needed to puncture the gloves. Level of protection given by gloves was compared to expected bite forces and tooth sharpness of bats. Cotton, plastic-coated synthetic fabric, and proprietary materials advertised as puncture- and cut-resistant were easy to penetrate compared to leather gloves. Split leather gives the highest level of protection, but with reduced dexterity. These are best for handling larger bats (>40 g) or if higher safety is preferred. Deerskin gives reasonable protection without much loss in dexterity for handling bats <40 g.