Secondary Sexual Variation Research Articles

Geographic variation in select species of the bat genus Platyrrhinus

The taxonomy of Neotropical bats is constantly changing, with new species being described and junior synonyms elevated, while other taxa are relegated to junior synonyms or subspecies. The genus Platyrrhinus has followed this trend, with some issues persisting about the current status of its subspecies. Here we evaluate variation in cranial shape and size based on geometric morphometric analyses of Platyrrhinus dorsalis and P. umbratus. P. dorsalis occurs at elevations from sea level to above 2,000 m and is found from southern Panama southward into Colombia and along both slopes of the Andes in Ecuador. P. umbratus occurs at elevations from 400 m to above 3,150 m in the Andean from Colombia south through Bolivia and Caribbean Mountain systems of Venezuela and Colombia. Our analyses did not support the recognition of subspecies in either species. The difference in skull size and shape between populations of P. dorsalis is associated with elevation, suggesting that this species exhibits an altitudinal clinal variation, with individuals being larger in the lower elevation and smaller in higher elevations. In P. umbratus the difference in skull size and shape between populations is associated with a latitudinal cline, with individuals tending to be larger in the northern part of their range. Our analyses did not reveal the existence of secondary sexual variation in P. dorsalis nor in P. umbratus.

Sharing the Space: Variation in Morphometric, Ecoregional, Migratory and Reproductive Patterns of Three Sympatric Artibeus Species

Bats of the phyllostomid genus Artibeus are primarily frugivorous, and they often are captured carrying the fruits of figs (Ficus spp.) or Cecropia spp. Although two or three species of Artibeus (sensu stricto) are found sympatrically in many regions of the Neotropics, little is known about the potential competitive interactions of these congeners in areas of sympatry. Competition might occur for food, roost sites, or other resources, and might be expressed as spatial or temporal partitioning in feeding or reproduction, as increased displacement of feeding- or foraging-related characters, or as some combination of these factors. These effects might be more pronounced near the distributional limits of the species, where resources might be more limited (both in abundance and diversity), and more patchily distributed. Three species of Artibeus (A. fimbriatus, A. lituratus, and A. planirostris), are at or near their southern or south-western distributional limits in Paraguay. Previous analyses in Paraguay have determined that A. lituratus and A. planirostris are migratory, with A. lituratus being most abundant during the wet season (October–February), and A. planirostris in the variable season (March–May). Artibeus fimbriatus and A. lituratus are relatively more abundant in the Atlantic Forest ecoregion; and A. planirostris in the Cerrado. In this study we examined morphometric variation in wing and craniomandibular characters, as well as reproductive patterns, to further explore the potential niche partitioning along these dimensions that may reduce competition for resources. We tested for morphometric differences among the species, and for geographic and secondary sexual variation in each of the three species. Both wing and craniodental characters vary significantly among species. Artibeus fimbriatus exhibits sexual dimorphism in only one cranial character, and A. lituratus shows sexual dimorphism in three craniodental characters and in all wing characters, whereas A. planirostris is not sexually dimorphic in any character. Weak geographic variation was found in craniodental characters in A. planirostris, and in wing characters in the other two species. Differences were also encountered in the three species' morphometric responses to temperature and precipitation parameters. Evaluating these differences in morphometric patterns in the context of ecoregional and seasonal associations, migratory status and reproductive patterns, we conclude that the three species mitigate competitive pressure through a complex partitioning of available niche space.

Características morfológicas y morfométricas de cinco especies de Criptotis (Mammalia:Soricomorpha)

Se examinaron ejemplares de cuatro especies monotípicas, Cryptotis mexicana (n = 48), C. obscura (n = 47),C. alticola (n = 8) y C. magna (n = 3); además, de una politípica, C. parva berlandieri (n = 1), C. p. pueblensis (n= 16) y C. p. soricina (n = 84). La gran mayoría del material proviene de localidades del centro de México, exceptolos de Cryptotis magna, C. obscura y C. p. berlandieri. Los ejemplares de C. mexicana, C. obscura y C. magnafueron recolectados en bosque mesófilo de montaña, los de C. alticola en bosque de Pinus sp. y Abies sp. y losde C. parva en bosque tropical y subtropical, mesófilo de montaña, bosque de Quercus sp. y bosques mixto depino-encino. Las medidas morfométricas de 25 variables externas, craneales y mandibulares se obtuvieron decada ejemplar. Las especies C. alticola, C. magna y C. parva se reconocieron con facilidad; sin embargo, en C.mexicana y en C. obscura se traslapan sus medidas pero se pudieron distinguir con el empleo de un AnálisisDiscriminante. Las medidas de C. magna fueron mayores que las de las otras cuatro especies, así como las deC. alticola en general lo fueron de C. mexicana, C. obscura y C. parva. La comparación de las medidas de C. p.pueblensis y C. p. soricina mostraron que las de la primera son mayores que las de la segunda. Variación sexualsecundaria se encontró solamente en C. p. soricina, en donde las hembras resultaron de mayores dimensionesque los machos. Se mencionan dos registros de simpatría entre C. obscura y C. parva y uno entre C. mexicanay C. parva.

Geographic Variation and Subspecific Status of the Swamp Rabbit (Sylvilagus aquaticus)

There has been some debate in the scientific literature on whether or not two subspecies of the swamp rabbit, Sylvilagus aquaticus aquaticus and S. a. littoralis, exist. The latter subspecies is believed to be restricted to habitats along the coast line of Texas, Louisiana, Mississippi, and Alabama. The objectives of this research were to record a standard set of cranial measurements from voucher specimens of the swamp rabbit that are housed in natural history collections and use multivariate statistics to assess the degree of geographic variation among populations throughout Louisiana. Morphological variation was assessed by taking 26 cranial measurements with a digital caliper and rounded to the nearest 0.01 mm. We performed analysis of variance (ANOVA) to determine the extent of secondary sexual variation and a multivariate analysis of variance (MANOVA) to detect differences in morphological variation among sampling units. Our results indicated no significant secondary sexual variation between male and...

Ecología y reproducción del murciélago Centurio senex (Chiroptera: Phyllostomidae) en Oaxaca, México

Wrinke-faced bat Centurio senex is a species with wide geographical distribution, but in those places where it has been recorded, its abundance is typically low, therefore it is considered a rare species and many ecological and reproductive aspects are anecdotic or derived from casual observations. In this study, we report some ecological data, such as sex ratio, age structure, reproductive pattern and its relation with rainfall, patterns of daily activity, as well as secondary sexual variation in weight and length of forearm of a population of C. senex studied for 16 months in a heterogeneous landscape in the Sierra Juarez of Oaxaca, Mexico.

THE FLORIDA BONNETED BAT, EUMOPS FLORIDANUS (CHIROPTERA: MOLOSSIDAE): DISTRIBUTION, MORPHOMETRICS, SYSTEMATICS, AND ECOLOGY

A review and reappraisal of bats of the genus Eumops (Chiroptera: Molossidae) reveals that considerable geographic variation is present in the bonneted bat, E. glaucinus; it is a complex consisting of .1 species. Bonneted bats in Florida are significantly larger than those in all other populations, and have proportionally shorter and deeper basisphenoid pits, the glenoid fossa is broadly triangular with rounded apices, and bacular shape differs from that in other populations. Additionally, bonneted bats in Florida have a broader palate than bats from populations in South America. Given these differences, the correct name for both Pleistocene and Recent Florida bonneted bats is Eumops floridanus (Allen, 1932). We found no geographic variation in Recent populations of Florida Eumops and little secondary sexual variation. We describe and review the distribution, morphometrics, systematics, ecology, and taxonomic history of the species, which is restricted to southern Florida. E. floridanus has one of the most restricted distributions of any bat in the New World and is one of the most critically endangered mammalian species in North America. The New World bonneted bats of the genus Eumops (Chiroptera: Molossidae) are a monophyletic lineage of 8‐10 species—E. auripendulus, E. bonariensis, E. dabbenei, E. glaucinus, E. hansae, E. maurus, E. patagonicus, E. perotis, E. trumbulli, and E. underwoodi (Eger 1977; Freeman 1981;

TAXONOMIC STATUS OFMYOTIS(CHIROPTERA: VESPERTILIONIDAE) IN PARAGUAY

Qualitative and quantitative variation in morphology was assessed for 6 species of Myotis from South America to determine which taxa occur in Paraguay, characteristics that allow for their discrimination, and the degree of geographic and secondary sexual variation that occurs in Paraguayan forms. Secondary sexual dimorphism and geographic variation were evaluated from univariate and multivariate perspectives. Multivariate morphometric differences in cranial morphology among taxa, independent of size, and mensural characters that best separate species were determined using principal components analysis followed by size-adjusted discriminant function analysis. Five species, M. albescens, M. nigricans, M. riparius, M. ruber, and M. simus, occur in Paraguay and can be distinguished using combinations of cranial and external characteristics. No significant sexual dimorphism or geographic variation was detected in these taxa of Myotis in Paraguay. M. levis has not been recorded for Paraguay as previously reported, but it may occur in the country. M. simus, a species previously considered to be restricted to the Amazon Basin, occurs as far south as Paraguay and northern Argentina. Although M. simus varies significantly in size across its range, highly differentiated cranial and external morphology allows for recognition of this species across its range.

VARIACION INTRAPOBLACIONAL E INTERPOBLACIONAL DE PEROMYSCUS INEIANOTÍS (RODENTIA: MURIDAE) EN EL EJE VOLCANICO TRANSVERSO, MEXICO

la variación no geográfica y geográfica de Peromyscus melanotís se estudia con base en el análisis de 1485 ejemplares de museo, procedentes de 125 localidades del Eje Volcánico Transverso de México. Por medio de técnicas univariantes y multivariantes se analizó el comportamiento de 25 caracteres morfométricos, 21 del cráneo y cuatro de la piel. la variación no geográfica comprende la variación ontogenética, variación sexual secundaria y variación de la coloración. Para el análisis ontogenético los individuos fueron agrupados en cinco categorías de edad. Se encontró que el valor cuantitativo de los caracteres aumenta con la edad y el estadio adulto se alcanza en la edad IV. la variación sexual secundaria muestra que en Peromyscus melanotís se presenta dimorfismo sexual secundario desde la edad juvenil. El dimorfismo es más evidente en la edad adulta en donde 14 de los 25 caracteres analizados se comportan como dimórficos, lo que determina que las hembras sean más grandes que los machos. la coloración de Peromyscus melanotis está relacionada con la edad del individuo y con la época del año. los jóvenes siempre presentan una coloración obscura en cualquier época y a medida que el individuo envejece se torna más clara. Durante el año se presentan dos fases de coloración bien marcadas, una obscura que corresponde a los individuos de verano y la clara a los de invierno. Para la variación geográfica sólo se consideraron los individuos adultos, de los que se analizaron 16 caracteres morfométricos y la coloración, estos especímenes proceden de una serie de localidades a lo largo de un transecto con orientación oeste-este, que empieza en el Cerro San Andrés, Michoacán y termina en el Pico de Orizaba, Veracruz. los resultados del análisis muestran que la mayoría de ios caracteres exhiben escasa variación geográfica, los ejemplares más grandes y de coloración más clara se encuentran en el centro del transecto, es decir, en el grupo Popocatépetl-Iztaccíhuatl, en tanto que hacia los extremos el tamaño tiende a disminuir y la coloración es más obscura.

Assessment of Morphometric Variation in Natural Populations: the Inadequacy of the Univariate Approach

Systematists often attempt to avoid the problem of correlated characters by estab- lishing an arbitrary number of variables that must be significant before groups are considered distinct. The appropriateness of this approach has not been evaluated empirically in the bio- logical literature. We analyzed morphometric data for 27 species of bats from the Brazilian Northeast. Twenty-two mensural characters (12 cranial, 10 external) were analyzed for interlo- cality and secondary sexual variation in each species using ANOVA and MANOVA. The uni- variate and multivariate analyses showed little correspondence; no predictable relationship between the number of characters exhibiting significance for a particular treatment effect in the univariate analyses and the significance level for that treatment in the multivariate analysis was discernible. Small sample sizes or disparate sample sizes do not contribute to this phenomenon. Results ranged from: 11 of 12 characters significant using ANOVA and nonsignificance in the MANOVA; to no character significant using the ANOVA with significance in the multivariate analysis. Because MANOVA utilizes rather than ignores correlations among characters, it is the correct statistical test for evaluating overall group differences. We show that even conselvative interpretations of the univariate results can lead to erroneous systematic conclusions. (Morpho- metric variation; MANOVA; multivariate statistics; ANOVA; univariate statistics; natural pop- ulations; Chiroptera; bats; Brazil.)

Systematic revision of the African mongoose genus Crossarchus (Mammalia: Viverridae)

Morphometric variation in external and cranial measurements of 152 specimens of Crossarchus was analyzed by means of univariate and multivariate statistical procedures. From the results of the analyses, four species of Crossarchus are recognized: C. obscurus from Sierra Leone to Ghana, C. alexandri from Zaire and Uganda, C. ansorgei known from the holotype from Angola and a second specimen from western Zaire, and Crossarchus platycephalus n. sp. from Cameroon, Nigeria, and Benin. Crossarchus obscurus and C. platycephalus are considered monotypic, whereas two subspecies are recognized in C. alexandri: C. alexandri alexandri from northern and central Zaire and C. alexandri minor n. ssp. from extreme eastern Zaire and Uganda. Significant secondary sexual variation was lacking in all taxa studied. Little individual variation was present in geographic samples. Geographic distributions of all taxa are plotted based upon specimens examined and literature records.

Geographic and secondary sexual variation in the morphology of Eptesicus fitscus

Geographic and secondary sexual variation in the morphology of Eptesicus fitscus

Intraisland and interisland variation in Antillean populations of Molossus molossus (Mammalia: Molossidae)

Significant levels of secondary sexual variation and expected levels of individual variation were demonstrated in all samples of Molossus molossus from Jamaica, Guadeloupe, and Trinidad examined with univariate analyses. Significant morphometric differences were demonstrated among samples of Molossus molossus that originated from geographically close localities on the same island. Using multivariate techniques, broader patterns of geographic variation were demonstrated among the Antillean populations of M. molossus.

Systematics and Evolution of the Pygmy Shrews (Subgenus Microsorex) of North America

Morphological and zoogeographical data indicate that North American pygmy shrews are referable to the Holarctic genus Sorex and to the Nearctic subgenus Microsorex Coues, 1877. Microsorex has its closest affinities with the North American autochthonous subgenus Otisorex . These subgeneric relationships are represented in a phylogenetic classification. Univariate and multivariate analyses support the conclusion that the subgenus Microsorex is monotypic, containing the species Sorex hoyi . Five subspecies are recognized based on these analyses. Variation in the species is generally that of decreased overall size from north to south. In addition, there are several zones where the species exhibits a rapid change in size. These zones demarcate subspecies boundaries. There is no demonstrable secondary sexual variation and individual variation is slight. There are significant changes in the skull and in the head and body length with increased age. The roots of the first upper incisors grow continuously, thus farther separating the cingulum from the alveolus with increased age. The degree of separation between the cingulum and alveolus is used as the index to age. Wear on the first upper incisors is rapid. Their continued down and back growth is necessary for continued occlusion with the lower incisors.

Variation within and among Populations of the Short-Tailed Shrew in Connecticut

Analyses of craniometric variance within a population of short-tailed shrews, Blarina brevicauda , in Connecticut revealed almost no secondary sexual variation or variation resulting from age and only moderate individual variation. Analyses of geographic variation demonstrated significant differences in cranial size between samples from the western and eastern extremes of Connecticut, but only a slight step in the cline was found in intervening areas. The possibility that the step denotes a zone of secondary intergradation was considered, but available data were judged inconclusive.

Notes on the Biology of the Central American Squirrel, Sciurus richmondi

Additional specimens of Sciurus richmondi are reported, along with comments on variation, distribution, reproduction and molt in this little kno.on squirrel. As presently understood, S. richmondi occurs only in the Caribbean rain forests of Nicaragua. Significant secondary sexual variation in adults was found only in zygomatic breadth, in which females are the larger. Available evidence reveals that the breeding season extends at least from February to September, and suggests two seasonal molts annually. INTRODUCTION Sciurus richmondi was named and described by Nelson (1898: 146), based on a series of specimens collected by Charles W. Richmond in 1892 on the Rio Escondido above Bluefields, Departamento Zelaya, Nicaragua. Subsequently, ]. A. Allen (1908:660; 1910: 104) recorded several specimens from the Caribbean drainage of central Nicaragua, but we are unaware of reports of additional material since Allen's second paper. In recent studies in Nicaragua, 53 specimens of S. richmondi have been collected, providing noteworthy data on the biology of this poorly known sciurid. VARIATION In the original description and in subsequent publications '(Nelson, 1899:101; Hall and Kelson, 1959:395), Sciurus richmondi has been characterized as closely related to S. granatensis, recorded from northern Costa Rica southward into South America. Nelson (1898: 147) supposed it probable that the two intergraded. S. richmondi differs principally from the North American subspecies of S. granatensis-hoffmanni of Costa Rica, chiriquensis of Costa Rica and Panama (these two represent but a single subspecies according to Harris, 1943:9-10) and morulus (choco, a synonym according to, Handley, 1966:777) of Panama-in being smaller, both externally and cranially, slightly less richly colored overall, and in having conspicuously paler bands on the hairs of the tail (tawny ochraceous as opposed to fulvous or buffy orange). We agree that richmondi resembles granatensis in general features and admit the possibility that the two may be found to be conspecific. Nevertheless, we are reluctant at this time to consider richmondi as a subspecies of granatensls because of the great size difference in the specimens available to us. The smallest adult granatensis that we have seen is a female '(KU 60478) from El Dragon, 26 km S San Jose, Costa Rica, in which the greatest length of skull is 53.1 mm, whereas the largest richmondi is a male from El Rccreo with a greatest length of skull of 51.5 mrn (Table 1). The only indication of possible intergradation now available between the two taxa is revealed by a male (skin only) from Cataratas San Carlos, Costa Rica (AMNH 141922), which differs from other Costa Rican granatensis in that both dorsal and ventral sides of the tail are considerably less reddish-orange; the tail of this specimen thus closely resembles those of our Nicaraguan squirrels 'in color. Jones & Genoways in American Midland Naturalist (July 1971) 86(1). Copyright 1971, University of Notre Dame. Used by permission.

Revision of the Pocket Mice, Perognathus penicillatus

The species Perognathus penicillatus is revised taxonomically. Eight subspecies are recognized and characterized. The subspecies P. penicillatus minimus is here referred to Perognathus intermedius . The type locality of P. p. penicillatus is redesignated. Age-variation, secondary sexual variation, and individual variation within the species are summarized. Intraspecific differentiation, clinal variation, and the importance of geographical barriers are discussed.

Revision of the Desert Cottontail, Sylvilagus audubonii, in the Southwest

Individual, secondary sexual and geographic variations are analyzed in Sylvilagus audubonii in the Southwest. Ways of distinguishing this species from both S. floridanus and S. nuttallii in this region are presented. A method of selecting homogeneity in age of specimens is suggested. Individual variation appears to be average and secondary sexual variation probably unimportant in most characters. Cranial and external characters are most useful in studying geographic variation while color, except in one subspecies, is of little significance. The geographic location of character shifts in 12 characters is shown graphically. Those shifts showing a high degree of concordancy form the primary basis for subspecific boundaries. Four subspecies of S. audubonii ( warreni, arizonae, minor and goldmani ) are recognized, and the name cedrophilus is placed in synonymy. Strong local variation occurring in certain subspecies is described. The Mogollon Plateau is shown to have been a most important geographic feature affecting the differentiation within this species in Arizona.

Age, Sex, and Weight Comparisons in Three Species of Shrews

The extreme variability in species of shrews has confused systematists for some time. Shrews were conceded to be more variable than most other mammalian groups and taxonomically extremely difficult to handle. Only relatively recently have the sources of this variability been recognized and analyzed. Several recent authors have studied growth and sexual patterns in Sorex and related genera. These studies establish that the so-called “inherent variability” of shrews is actually no greater than that of many mammalian groups once growth and secondary sexual variation are understood. When ample specimens for comparison are available, these sources of variation cause little difficulty. The small size and the difficulty of obtaining specimens in many areas remain as the chief deterrents to full understanding of the systematics of Sorex . The material presented in this paper was collected in connection with a study of differentiation in restricted populations of tidal marsh shrews in the San Francisco Bay Region. In order to compare morphological traits of several shrew populations statistically, variability due to age, sex and size (as reflected by weight) had necessarily to be considered first. Variation arising from these factors had to be eliminated or minimized before reliable trait samples could be defined and compared. This paper reports the variability of these characteristics for the individual species populations and presents data in a manner to facilitate comparisons between species. The differentiation pattern in the shrew populations under study will be presented in a later paper. Only specimens from the San Francisco Bay Region are included. The “Bay Region” is composed of nine counties—Santa Clara, San Mateo, San Francisco, Marin, Sonoma, Napa, Solano, Contra Costa, and Alameda. All specimens from these counties for which full data were available (692) have been utilized. A number …