INDIVIDUAL- AND POPULATION-LEVEL RESPONSES OF A KEYSTONE PREDATOR TO GEOGRAPHIC VARIATION IN PREY

Abstract ContextThe invasive cane toad (Rhinella marina) has decimated populations of a keystone predator, the yellow-spotted monitor (Varanus panoptes), causing trophic cascades in Australian animal communities. Paradoxically, some V. panoptes populations coexist with toads. Demonstrating patterns in heterogeneous population-level impacts could reveal mechanisms that mediate individual effects, and provide managers with the ability to predict future impacts and assist in population recovery. AimsThe aim of the present study was to search for spatial patterns of population resilience of V. panoptes to invasive cane toads. MethodsPublished literature, unpublished data, reports and anecdotal information from trained herpetologists were used to test the emerging hypothesis that resilient predator populations are mainly coastal, whereas non-resilient populations are mostly inland. Key resultsPost-toad invasion data from 23 V. panoptes populations supported the idea that toad impacts on V. panoptes were heterogeneous; roughly half the populations could be designated as resilient (n=13) and half as non-resilient (n=10). Resilient populations had longer times since toad invasion than did non-resilient populations (39 versus 9 years respectively), supporting the idea that some recovery can occur. Non-resilient populations were exclusively inland (n=10), whereas resilient populations were split between inland (n=5) and coastal (n=8) populations. Resilient inland populations, however, were mainly confined to areas in which decades had passed since toad invasion. ConclusionsThe findings suggest that coastal V. panoptes populations fare much better than inland populations when it comes to surviving invading cane toads. ImplicationsUnambiguous recovery of monitor populations remains undemonstrated and will require long-term population monitoring before and after toad invasion.

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Consequences and causes of geographic variation in the body size of a keystone predator,Notophthalmus viridescens

Oecologia ◽

10.1007/bf00627739 ◽

1994 ◽

Vol 99 (3-4) ◽

pp. 271-280 ◽

Cited By ~ 14

Author(s):

Lynn M. Kurzava ◽

Peter J. Morin

Keyword(s):

Body Size ◽

Geographic Variation ◽

The Body ◽

Notophthalmus Viridescens ◽

Keystone Predator

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Source-sink dynamics could sustain HIV epidemics in rural communities in sub-Saharan Africa: the case of Malawi

10.1101/468298 ◽

2018 ◽

Author(s):

Justin T. Okano ◽

Katie Sharp ◽

Laurence Palk ◽

Sally Blower

Keyword(s):

Rural Communities ◽

Geographic Variation ◽

Rural Areas ◽

Population Level ◽

Hiv Prevalence ◽

Sub Saharan Africa ◽

Heterosexual Transmission ◽

Urban Centers ◽

Mobility Data ◽

Sub Saharan

AbstractBackground:Approximately 25.5 million individuals are infected with HIV in sub-Saharan Africa (SSA). Epidemics in this region are generalized, show substantial geographic variation in prevalence, and are driven by heterosexual transmission; populations are highly mobile. We propose that generalized HIV epidemics should be viewed as a series of micro-epidemics occurring in multiple connected communities. Using a mathematical model, we test the hypothesis that travel can sustain HIV micro-epidemics in communities where transmission is too low to be self-sustaining. We use Malawi as a case study.Methods:We first conduct a mapping exercise to visualize geographic variation in HIV prevalence and population-level mobility. We construct maps by spatially interpolating georeferenced HIV-testing and mobility data from a nationally representative population-level survey: the 2015-16 Malawi Demographic and Health Survey. To test our hypothesis, we construct a novel HIV epidemic model that includes three transmission pathways: resident-to-resident, visitor-caused and travel-related. The model consists of communities functioning as “sources” and “sinks”. A community is a source if transmission is high enough to be self-sustaining, and a sink if it is not.Results:HIV prevalence ranges from zero to 27%. Mobility is high, 27% of the population took a trip lasting at least a month in the previous year. Prevalence is higher in urban centers than rural areas, but long-duration travel is higher in rural areas than urban centers. We show that a source-community can sustain a micro-epidemic in a sink-community, but only if specific epidemiological and demographic threshold conditions are met. The threshold depends upon the level of transmission in the source- and sink-communities, as well as the relative sizes of the two communities. The larger the source than the sink, the lower transmission in the source-community needs to be for sustainability.Discussion:Our results support our hypothesis, and suggest that it may be rather easy for large urban communities to sustain HIV micro-epidemics in small rural communities; this may be occurring in northern Malawi. Visitor-generated and travel-related transmission may also be sustaining micro-epidemics in rural communities in other SSA countries with highly-mobile populations. It is essential to consider mobility when developing HIV elimination strategies.

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Objectively measuring subjectively described traits: geographic variation in body shape and caudal coloration pattern within Vieja melanura (Teleostei: Cichlidae)

Revista de Biología Tropical ◽

10.15517/rbt.v65i2.25500 ◽

2017 ◽

Vol 65 (2) ◽

Cited By ~ 2

Author(s):

Caleb D. McMahan ◽

Justin Kutz ◽

Christopher Murray ◽

Prosanta Chakrabarty ◽

Aaron Geheber ◽

...

Keyword(s):

Geographic Variation ◽

Body Shape ◽

Population Level ◽

Phylogeographic Structure ◽

Shape Variation ◽

Southern Mexico ◽

Geometric Morphometric ◽

Morphometric Analyses ◽

Mitochondrial Cytochrome B ◽

Riverine Habitats

Vieja melanura is a Neotropical cichlid occurring in the Petén-lake district systems of Guatemala, as well as the Río Grijalva-Usumacinta basin, and other systems in Southern México, Belize, and Guatemala. A caudal stripe, extending forward from the caudal peduncle, is characteristic of this species. This stripe is sloped downward in nearly all individuals of V. melanura, but the degree of the slope is highly variable throughout its range. The slope and shape of the stripe has previously been used in diagnosing and differentiating between species of Vieja. The purpose of this study was to use objective methods to investigate morphological variation in the caudal stripe and body shape throughout the range of V. melanura. We studied geometric morphometric analyses of body shape and empirical measurements of the slope of the caudal stripe in 215 specimens of V. melanura. We also used the mitochondrial cytochrome b marker to study population level patterns within V. melanura. Results from our analyses showed significant geographic variation in body shape and patterns of coloration with little mitochondrial phylogeographic structure. These patterns likely correspond to differences in riverine habitats throughout the species’ distribution. In conclusion, these results can be used to inform other studies of color and shape variation as it applies to taxonomy and systematics.

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