Spatial heterogeneity of habitat suitability for Rift Valley fever occurrence in Tanzania: an ecological niche modelling approach

Despite the long history of Rift Valley fever (RVF) in Tanzania, extent of its suitable habitat in the country remains unclear. In this study we investigated potential effects of temperature, precipitation, elevation, soil type, livestock density, rainfall pattern, proximity to wild animals, protected areas and forest on the habitat suitability for RVF occurrence in Tanzania. Presence-only records of 193 RVF outbreak locations from 1930 to 2007 together with potential predictor variables were used to model and map the suitable habitats for RVF occurrence using ecological niche modelling. Ground-truthing of the model outputs was conducted by comparing the levels of RVF virus specific antibodies in cattle, sheep and goats sampled from locations in Tanzania that presented different predicted habitat suitability values. Habitat suitability values for RVF occurrence were higher in the northern and central-eastern regions of Tanzania than the rest of the regions in the country. Soil type and precipitation of the wettest quarter contributed equally to habitat suitability (32.4% each), followed by livestock density (25.9%) and rainfall pattern (9.3%). Ground-truthing of model outputs revealed that the odds of an animal being seropositive for RVFV when sampled from areas predicted to be most suitable for RVF occurrence were twice the odds of an animal sampled from areas least suitable for RVF occurrence (95% CI: 1.43, 2.76, p < 0.001). The regions in the northern and central-eastern Tanzania were more suitable for RVF occurrence than the rest of the regions in the country. The modelled suitable habitat is characterised by impermeable soils, moderate precipitation in the wettest quarter, high livestock density and a bimodal rainfall pattern. The findings of this study should provide guidance for the design of appropriate RVF surveillance, prevention and control strategies which target areas with these characteristics

Disentangling the dynamics of invasive fireweed (Senecio madagascariensis Poir. species complex) in the Hawaiian Islands

The original publication is available at http://link.springer.com/journal/10530Studies investigating the genetic variation of invasive species render opportunities to better understand the dynamics of biological invasions from an ecological and evolutionary perspective. In this study, we investigate fine-scale population genetic structure of invasive Senecio madagascariensis (fireweed) using microsatellite markers to determine levels of genetic diversity and how it pertains to introduction history of this species within and among the Hawaiian Islands. Dispersal patterns were interpreted and, together with a habitat suitability analysis, we aim to describe the potential range expansion of S. madgascariensis within the islands. Bayesian and frequency-based analyses revealed genetic structure with two major genetic demes corresponding to the two fireweed-infested islands of Maui and Hawaii. Both these demes showed further genetic sub-structure, each consisting of three genetically distinct subgroups. Overall, fireweed showed significant levels of inbreeding. Major genetic demes (Maui and Hawaii) differed in observed heterozygosities, inbreeding and genetic structure, each harbouring a large proportion of private alleles. In contrast to the current understanding of fireweed's introduction history between the Hawaiian Islands, fine-scale population genetic parameters suggest that this species has been introduced at least twice, possibly even more, to the archipelago. Spatial analyses also revealed high correlation between genetic similarity and geographical proximity (>2 km apart) followed by a sharp decline. In addition, a single population was identified that likely resulted from a rare human- or animal-mediated extreme long-distance dispersal event from Maui to Hawaii. Bayesian and likelihood estimates of 'first generation migrants' also concurred that contemporary dispersal occurs more frequently over smaller spatial scales than larger scales. These findings indicate that spread in this species occurs primarily via a stratified strategy. Predictions from habitat suitability models indicate all Hawaiian Islands as highly suitable for fireweed invasion and the movement of propagules to currently uninfested islands and outlying suitable habitats should be avoided to circumvent further expansions of the invasion. © 2009 Springer Science+Business Media B.V.Post-prin

Opogona sacchari (Lepidoptera: Tineidae), a New Pest of Pineapple in Hawaii

Scientific note.This note is the first report of recent infestations of pineapple by Opogona sacchari in Hawaii. Brief notes on damage levels inflicted by O. sacchari on pineapple are reported

A simple but novel approach to calculate seabird light fallout: A case study from Kauaʻi

Injury and mortality of night flying seabirds due to lights (fallout) affects their long-term viability. However, the cryptic nature of these species hinders direct estimates and projections of fallout. The Kauaʻi Seabird Habitat Conservation Plan (KSHCP) characterizes the current and projected fallout for Newell's shearwaters (Puffinus auricularis newelli), Hawaiian petrels (Pterodroma sandwichensis) and the Hawaiʻi distinct population segment of the band-rumped storm-petrels (Oceanodroma castro) on the island of Kauaʻi across eight permittees. In the KSHCP, each permittee was required to itemize the lighting infrastructure related to their facilities (type, wattage, number of lights, etc.) as well as supply an overall expected seabird fallout number with an estimate of detection probability or ability to find the fallout birds. Light intensity is thought to be correlated to the degree of attraction to a light source. Here we identify seabird fallout using indirect estimates derived from the KSHCP and present a reproducible method to consistently project and calculate fallout between entities that need to reduce seabird mortality due to their light sources. Though the permittees did not provide an estimate of light intensity at their sites, we extrapolated luminous intensity (light brightness) from their itemized light information (i.e., lumens/watt). Using luminous intensity, we then derived the degree of fallout per lumen and its variation across the permittees. As a proof of concept, we then projected the fallout per lumen estimate onto streetlights owned by the Kauaʻi Island Utility Cooperative, as applied over a range of detectability correction factors. Though fallout varies significantly based on the detectability correction factor used, when considering the site differences on Kauaʻi, a previous fallout estimate, and the overlapping characteristics of the projected versus actual luminous intensities, the utilities projected fallout appears applicable. We feel that the methodology can be used as a baseline to infer fallout associated with various entities

Modeling the Habitat Retreat of the Rediscovered Endemic Hawaiian Moth <em>Omiodes continuatalis</em> Wallengren (Lepidoptera: Crambidae)

<div><p>Survey data over the last 100 years indicate that populations of the endemic Hawaiian leafroller moth, <em>Omiodes continuatalis</em> (Wallengren) (Lepidoptera: Crambidae), have declined, and the species is extirpated from large portions of its original range. Declines have been attributed largely to the invasion of non-native parasitoid species into Hawaiian ecosystems. To quantify changes in <em>O. continuatalis</em> distribution, we applied the maximum entropy modeling approach using Maxent. The model referenced historical (1892–1967) and current (2004–2008) survey data, to create predictive habitat suitability maps which illustrate the probability of occurrence of <em>O. continuatalis</em> based on historical data as contrasted with recent survey results. Probability of occurrence is predicted based on the association of biotic (vegetation) and abiotic (proxy of precipitation, proxy of temperature, elevation) environmental factors with 141 recent and historic survey locations, 38 of which <em>O. continuatalis</em> were collected from. Models built from the historical and recent surveys suggest habitat suitable for <em>O. continuatalis</em> has changed significantly over time, decreasing both in quantity and quality. We reference these data to examine the potential effects of non-native parasitoids as a factor in changing habitat suitability and range contraction for <em>O. continuatalis</em>. Synthesis and applications: Our results suggest that the range of <em>O. continuatalis</em>, an endemic Hawaiian species of conservation concern, has shrunk as its environment has degraded. Although few range shifts have been previously demonstrated in insects, such contractions caused by pressure from introduced species may be important factors in insect extinctions.</p> </div

The Ecological Niche Models (ENM) defined in Maxent showing the distribution of <i>O. continuatialis</i> as collected from 1892 to 1967 and projected onto a set of biotic and abiotic variables.

<p>The figure shows the historically defined ENM (A) along with that of the ENM projected 2050 (B). The 2050 GFDL 2.1 climate change model was used to derive projected future climate variables. As compared to the historic distribution (A) the 2050 projected distribution of historic data (B) shows an expansion of suitable habitat area (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051885#pone-0051885-t004" target="_blank">Table 4</a>). Although the trend of habitat expansion is similar to the contemporary (current and projected) models, the overall model prediction differs significantly (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051885#pone-0051885-t002" target="_blank">Table 2</a>).</p

The Levin's Niche breadth analysis outputs a scale of specialization between 0 and 1, where “0” is a specialist and “1” is a generalist.

<p>Here, niche breadth is used as a measure of the association to the environmental variables over time. Interestingly, the contemporary current and projected distribution of <i>O. continuatalis</i> shows lower niche specificity than does the historic distribution.</p

The Ecological Niche Models (ENM) defined in Maxent showing the distribution of <i>O. continuatialis</i> as collected from 2004 to 2010 and projected onto a set of biotic and abiotic variables.

<p>The figure shows the current ENM (A) along with that of the ENM projected into 2050 (B). The 2050 GFDL 2.1 climate change model was used to derive projected future climate variables. As compared to the current distribution (A) the 2050 projected distribution (B) shows an expansion of suitable habitat area (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051885#pone-0051885-t004" target="_blank">Table 4</a>).</p

Map of historic and current <i>O. continuatalis</i> presence localities collected from around the Hawaiian Islands, as well as light trap collection localities where <i>O. continuatalis</i> were not observed during current surveys.

<p>These points were used to develop the Ecological Niche Models for each time period.</p