Ecology and Evolutionary Biology Commons^™

Distribución Geográfica De La Fauna De Anfibios Del Uruguay, Diego Nuñez, Raúl Maneyro, José A. Langone, Rafael O. De Sá

Biology Faculty Publications

Datos precises sobre la distribución geográfica de los organismos de una región son necesarios y prerrequisito para entender las interrelaciones ecológicas entre las comunidades biológicas. Esta información también contribuye a entender el componente histórico de la región posibilitando la determinación de centros de origen y el establecimiento de patrones de diversidad (Ron, 2000), así mismo posibilita realizar inferencias acerca de los mecanismos de especiación en los diferentes grupos zoológicos (Bridarolli & Di Tada, 1994).

La distribución geográfica de los anfibios en Uruguay ha sido parcialmente reportada (Achaval & Olmos, 1997; Langone, 1995; Maneyro et al, 1995; Maneyro & Langone, 2001). …

Características Histológicas De La Tumefacción Frontal De Melanophryniscus (Amphibia: Anura: Bufonidae), Daniel E. Naya, José A. Langone, Rafael O. De Sá

Biology Faculty Publications

Se analizó la histología tegumentaria de la región cefálica en seis especies del género Melanophryniscus, pertenecientes a los grupos stelzneri (4) y tumifrons (2), con el objetivo de esclarecer la estructura de la tumefacción frontal y su posible función. Las características generales de la histología del grupo stelzneri, coincidieron con las descripciones tegumentarias existentes para el género. Sin embargo, la región cefálica frontal en las dos especies del grupo tumifrons muestran cambios histológicos correlacionados a la tumefacción frontal. Esta estructura presenta una organización similar a otras macroglándulas presentes en la dermis de anuros (e.g., parotoides, paracnémicas), y por tanto se …

On The Engimatic Distribution Of The Honduran Endemic Leptodactylus Silvanimbus (Amphibia: Anura: Leptodactylidae), W. R. Heyer, Rafael O. De Sá, Sarah Muller

Biology Faculty Publications

Most species of the frog genus Leptodactylus occur in South America, and all authors who have treated the zoogeography of the genus have concluded that it originated somewhere in South America (e.g., Savage 1982). Savage (1982, 518) summarized the historical herpetofaunal units of the Neotropics as follows: "All evidence points to an ancient contiguity and essential similarity of a generalized tropical herpetofauna that ranged over tropical North, Middle, and most of South America in Cretaceous-Paleocene times. Descendents of this fauna are represented today by the South and Middle American tracks (Elements). To the north of this fauna ranged a subtropical-temperate …

Stage-Specific And Interactive Effects Of Sedimentation And Trout On A Headwater Stream Salamander, Winsor H. Lowe, Keith H. Nislow, Douglas T. Bolger

Dartmouth Scholarship

In species with complex life cycles, stage-specific effects of environmental conditions combine with factors regulating stage-specific recruitment to determine population-level response to habitat disturbance. The abundance of the stream salamander Gyrinophilus porphyriticus(Plethodontidae) is negatively related to both logging-associated sedimentation and brook trout (Salvelinus fontinalis) in headwater streams throughout New Hampshire, USA. To understand the mechanisms underlying these patterns, we investigated stage-specific and interactive effects of sedimentation and brook trout on G. porphyriticus. We conducted quantitative surveys of salamanders, brook trout, and substrate embeddedness in 15 first-order streams and used a controlled experiment to test the direct and interactive effects of …

On The Cranial Anatomy Of The Polycotylid Plesiosaurs, Including New Material Of Polycotylus Latipinnis, Cope, From Alabama, F. Robin O’Keefe

Biological Sciences Faculty Research

The cranial anatomy of plesiosaurs in the family Polycotylidae (Reptilia: Sauropterygia) has received renewed attention recently because various skull characters are thought to indicate plesiosauroid, rather than pliosauroid, affinities for this family. New data on the cranial anatomy of polycotylid plesiosaurs is presented, and is shown to compare closely to the structure of cryptocleidoid plesiosaurs. The morphology of known polycotylid taxa is reported and discussed, and a preliminary phylogenetic analysis is used to establish ingroup relationships of the Cryptocleidoidea. This study also presents new material referable to Polycotylus latipinnis from the Mooreville Chalk Formation of Alabama. This skeleton is largely …

The Effect Of Size-Limited Brood Capacity On Brood Size In A Freshwater Bivalve, Mark Beekey

Biology Faculty Publications

Size limited brood capacity is common among species with hard exoskeletons or shells. In these species, brood size is limited by the physical capacity to hold offspring. Here we present evidence that brood size is limited by physical constraints in Sphaerium striatinum , a small brooding bivalve. Sphaerium striatinum is a sequential brooder and produces offspring throughout the year. Offspring are brooded in marsupial sacs located on the inner demibranch. In an unconstrained brooder one would predict that brood size would increase as a function of adult length cubed, a volumetric relationship. In S. striatinum, brood size increases as less …

Light Dependence Of Selenium Uptake By Phytoplankton And Implications For Predicting Selenium Incorporation Into Food Webs, Stephen B. Baines, Nicholas S. Fisher, Martina A. Doblin, Gregory A. Cutter, Lynda S. Cutter, Brian Cole

OES Faculty Publications

The potentially toxic element selenium is first concentrated from solution to a large but highly variable degree by algae and bacteria before being passed on to consumers. The large loads of abiotic and detrital suspended particles often present in rivers and estuaries may obscure spatial and temporal patterns in Se concentrations at the base of the food web. We used radiotracers to estimate uptake of both selenite (Se(IV)) and C by intact plankton communities at two sites in the Sacramento/San Joaquin River Delta. Our goals were to determine (1) whether C and Se(IV) uptake were coupled, (2) the role of …

Dinitrogen Fixation And Release Of Ammonium And Dissolved Organic Nitrogen By Trichodesmium Ims101, Margaret R. Mulholland, Deborah A. Bronk, Douglas G. Capone

OES Faculty Publications

Two methods used to measure dinitrogen (N₂) fixation (acetylene reduction and ¹⁵N₂ uptake) often result in different N₂ fixation rates. Part of the discrepancy may arise from the observation that Trichodesmium can release a fraction of their recently fixed N₂ as dissolved organic nitrogen (DON) and/or ammonium (NH4 ⁺). To resolve outstanding issues regarding N₂ fixation and the production of dissolved combined nitrogen (N) by Trichodesmium, we conducted a comprehensive analysis of N₂ fixation and the production of DON and NH₄⁺ in cultures of Trichodesmium IMS101. We performed …

Does Antarctic Krill Employ Body Shrinkage As An Overwintering Strategy?, Se-Jong Ju, H. Rodger Harvey, H. C. Shinn, Y. Kim, S. H. Kang

OES Faculty Publications

To determine if Antarctic krill employ body shrinkage as one of its overwintering mechanisms in the field, Euphausia superba and Euphausia crystallorophias were collected during fall and winter in and around Marguerite Bay through US Southern Ocean GLOBEC field programs during fall and winter 2001 and 2002. The relationships between the body length and weight of both krill species were exponentially correlated with no significant differences between the two species (p>0.05). The ratio between eye diameter and body length of individual krill was examined in an expectation that it could be used as an indicator of the body shrinkage …

Beach-Cast Wrack As A Determinant Of Macroinvertebrate Assemblages And Trophic Subsidy To Sandy Beach Ecosystems, Rebecca Ince

Theses : Honours

The transport of detached macrophytes from seagrass meadows and reefs, otherwise known as wrack, has been identified in some parts of the world as a marine subsidy which can increase the productivity of coastal ecosystems. The aim of this study was to determine whether wrack deposits act as a marine subsidy on sandy beaches in Perth, by determining whether it influences the structure of, and is a source of nutrient to, the macroinvertebrate communities in this ecosystem. This was achieved by examining the abundance, composition and nutrient source of macrofauna, including epifauna, infauna and flying fauna, on three sandy beaches …

The Selfish Nature Of Generosity: Harassment And Food Sharing In Primates, Jeffrey R. Stevens

Jeffrey Stevens Publications

Animals may share food to gain immediate or delayed fitness benefits. Previous studies of sharing have concentrated on delayed benefits such as reciprocity, trade and punishment. This study tests an alternative model (the harassment or sharing–under–pressure hypothesis) in which a food owner immediately benefits because sharing avoids costly harassment from a beggar. I present an experiment that varies the potential ability of the beggar to harass, and of the owner to defend the food, to examine the effects of harassment on food sharing in two primate species: chimpanzees (Pan troglodytes) and squirrel monkeys (Saimiri boliviensis). For …

A Conceptual Framework For Non-Kin Food Sharing: Timing And Currency Of Benefits, Jeffrey R. Stevens, Ian C. Gilby

Jeffrey Stevens Publications

Many animal species, from arthropods to apes, share food. This paper presents a new framework that categorizes nonkin food sharing according to two axes: (1) the interval between sharing and receiving the benefits of sharing, and (2) the currency units in which benefits accrue to the sharer (especially food versus nonfood). Sharers can obtain immediate benefits from increased foraging efficiency, predation avoidance, mate provisioning, or manipulative mutualism. Reciprocity, trade, status enhancement and group augmentation can delay benefits. When benefits are delayed or when food is exchanged for nonfood benefits, maintaining sharing can become more difficult because animals face discounting and …

Record High Wolf, Canis Lupus, Pack Density, L. David Mech, Shawn Tracy

United States Geological Survey, Northern Prairie Wildlife Research Center: Publications

This report documents a year-around Wolf (Canis lupus) density of 18.2/100 km² and a summer density of 30.8/100 km², in a northeastern Minnesota Wolf pack. The previous record was a summer density of 14.1/100 km², for a Wolf pack on Vancouver Island, British Columbia, Canada.

Demographic Estimates From Y Chromosome Microsatellite Polymorphisms: Analysis Of A Worldwide Sample, J. Michael Macpherson, Sohini Ramachandran, Lisa Diamond, Marcus W. Feldman

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Polymorphisms in microsatellites on the human Y chromosome have been used to estimate important demographic parameters of human history. We compare two coalescent-based statistical methods that give estimates for a number of demographic parameters using the seven Y chromosome polymorphisms in the HGDP-CEPH Cell Line Panel, a collection of samples from 52 worldwide populations. The estimates for the time to the most recent common ancestor vary according to the method used and the assumptions about the prior distributions of model parameters, but are generally consistent with other global Y chromosome studies. We explore the sensitivity of these results to assumptions …

The Role Of Farm Dams As Refugia For Aquatic Invertebrates In A Salinised Landscape, South Western Australia, Jean-Michel Benier

Theses: Doctorates and Masters

In a salinised landscape farm dams may represent the last truly freshwater surface resource, and therefore provide refuge habitats for the biota of wetlands affected by increasing salinity. One wetland threatened by increased salinity in south-west Western Australia is Lake Toolibin. It is listed as a Wetland of International Importance under the Ramsar Convention in recognition of its high conservation value, and remediation actions to halt (and possibly reverse) further increases in salinity are being undertaken at this wetland. Farm dams act as aquatic refugia if they convey resistance and/or resilience to the biotic communities of a disturbed habitat. This …

In Vitro Propagation Of Some Western Australian Seagrasses, Julia Wilson

Theses: Doctorates and Masters

The development of a successful protocol for micropropagating seagrass provides a valuable tool for seagrass-restoration programs and a facility to study their biology (especially their physiology). This work reports on some of the culture requirements of some seagrasses that are commonly found in Western Australia: Posidonia coriacea, P. sinuosa, P. australis and Halophila ovalis. The protocol developed for H. ovalis allows very rapid multiplication and sustainable growth of cultures while the protocol developed for Posidonia requires further development. The culture of Posidonia cariacea proved to be problematic however experimental media that provided insights into its culture conditions. The carbohydrate source …