Many previous studies have attempted to assess ecological niche modeling performance using receiver operating characteristic (ROC) approaches, even though diverse problems with this metric have been pointed out in the literature. We explored different evaluation metrics based on independent testing data using the Darwin's Fox (Lycalopex fulvipes) as a detailed case in point. Six ecological niche models (ENMs; generalized linear models, boosted regression trees, Maxent, GARP, multivariable kernel density estimation, and NicheA) were explored and tested using six evaluation metrics (partial ROC, Akaike information criterion, omission rate, cumulative binomial probability), including two novel metrics to quantify model extrapolation versus interpolation (E‐space index I) and extent of extrapolation versus Jaccard similarity (E‐space index II). Different ENMs showed diverse and mixed performance, depending on the evaluation metric used. Because ENMs performed differently according to the evaluation metric employed, model selection should be based on the data available, assumptions necessary, and the particular research question. The typical ROC AUC evaluation approach should be discontinued when only presence data are available, and evaluations in environmental dimensions should be adopted as part of the toolkit of ENM researchers. Our results suggest that selecting Maxent ENM based solely on previous reports of its performance is a questionable practice. Instead, model comparisons, including diverse algorithms and parameterizations, should be the sine qua non for every study using ecological niche modeling. ENM evaluations should be developed using metrics that assess desired model characteristics instead of single measurement of fit between model and data. The metrics proposed herein that assess model performance in environmental space (i.e., E‐space indices I and II) may complement current methods for ENM evaluation.
The co-occurrence of domestic cats (Felis silvestris catus) and wild felids in rural landscapes can facilitate pathogen transmission. However, in the relatively-isolated regions of southern South America there have been no comprehensive studies to assess disease transmission risks between domestic cats and forest-dwelling wild felids such as guigna (Leopardus guigna). We evaluated hemoplasma infection and the possibility of transmission between domestic cats and guignas by comparing spatial and phylogenetic patterns of pathogen prevalence. Blood/spleen samples were collected from 102 wild guignas and 262 co-occurring rural domestic cats across the entire distribution range of guigna in Chile. Hemoplasma infection was assessed by direct sequencing of the 16S RNA gene. Infection with hemoplasmas was common and geographically widespread across different bioclimatic areas for both species. The most common feline Mycoplasma species in guigna and domestic cats were Candidatus M. haemominutum (CMhm) (15.7% guigna; 10.3% domestic cat) and Mycoplasma haemofelis (Mhf) (9.8% guigna, 6.1% domestic cat). A previously undescribed Mycoplasma sp. sequence was found in two guignas and one cat. Continuous forest-landscapes were associated with higher hemoplasma-prevalence in guignas. Shared hemoplasma nucleotide sequence types between guigna and domestic cats were rare, suggesting that cross-species transmission between guignas and domestic cats may occur, but is probably uncommon. Ectoparasites, which have been linked with hemoplasma transmission, were not found on guignas and were infrequent on domestic cats. Our results suggest that transmission pathways vary among hemoplasma species and, contrary to our predictions, domestic cats did not appear to be the main driver of hemoplasma infection in guignas in these human-dominated landscapes.
Mycoplasma haemocanis is prevalent in the endangered Darwin’s fox (Lycalopex fulvipes) in its main stronghold, Chiloé Island (Chile). The origin of the infection, its dynamics, its presence in other fox populations and the potential consequences for fox health remain unexplored. For 8 years, hemoplasmal DNA was screened and characterized in blood from 82 foxes in Chiloé and two other fox populations and in 250 free-ranging dogs from Chiloé. The prevalence of M. haemocanis in foxes was constant during the study years, and coinfection with “Candidatus Mycoplasma haematoparvum” was confirmed in 30% of the foxes. Both hemoplasma species were detected in the two mainland fox populations and in Chiloé dogs. M. haemocanis was significantly more prevalent and more genetically diverse in foxes than in dogs. Two of the seven M. haemocanis haplotypes identified were shared between these species. Network analyses did not show genetic structure by species (foxes versus dogs), geographic (island versus mainland populations), or temporal (years of study) factors. The probability of infection with M. haemocanis increased with fox age but was not associated with sex, season, or degree of anthropization of individual fox habitats. Some foxes recaptured years apart were infected with the same haplotype in both events, and no hematological alterations were associated with hemoplasma infection, suggesting tolerance to the infection. Altogether, our results indicate that M. haemocanis is enzootic in the Darwin’s fox and that intraspecific transmission is predominant. Nevertheless, such a prevalent pathogen in a threatened species represents a concern that must be considered in conservation actions.
IMPORTANCE Mycoplasma haemocanis is enzootic in Darwin’s foxes. There is a higher M. haemocanis genetic diversity and prevalence in foxes than in sympatric dogs, although haplotypes are shared between the two carnivore species. There is an apparent tolerance of Darwin’s foxes to Mycoplasma haemocanis.
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