Amphibian populations are globally declining at an alarming rate, and infectious diseases are amo... more Amphibian populations are globally declining at an alarming rate, and infectious diseases are among the main causes of their decline. Two micro-parasites, the fungus Batrachochytrium dendrobatidis (Bd) and the virus Ranavirus (RV) have caused mass mortality of amphibians and population declines. Other, less understood epizootics are caused by macro-parasites, such as Trombiculoidea chiggers. Infection with chiggers can affect frog behavior and survival. Furthermore, synergistic effects of co-infection with both macro and micro-parasites may lead to higher morbidity. To better understand these potential synergies, we investigated the presence and co-infection by chiggers, Bd and RV in the endemic frog Tlalocohyla smithii (T. smithii). Co-infection of Bd, RV, and/or chiggers is expected in habitats that are suitable for their co-occurrence; and if infection with one parasite facilitates infection with the others. On the other hand, co-infection could decrease if these parasites were to differ in their micro-environmental requirements (i.e. niche apportionment). A total of 116 frogs of T. smithii were studied during 2014 and 2016 in three streams within the Chamela-Cuixmala Biosphere Reserve in Jalisco, Mexico. Our results show that 31% of the frogs were infected with Trombiculoidea chiggers (Hannemania sp. and Eutrombicula alfreddugesi); Hannemania prevalence increased with air temperature and decreased in sites with high canopies and with water pH values above 8.5 and below 6.7. Bd prevalence was 2.6%, RV prevalence was 0%, and none of the frogs infected with chiggers were co-infected with Bd. Together, this study suggests that chiggers do not facilitate infection with Bd, as these are apportioned in different micro-habitats. Nevertheless, the statistical power to assure this is low. We recommend further epidemiological monitoring of multiple parasites in different geographical locations in order to provide insight on the true hazards, risks and conservation options for amphibian populations.
The Least Tern (Sterna antillarum) is broadly distributed in the United States, with three well-d... more The Least Tern (Sterna antillarum) is broadly distributed in the United States, with three well-defined sub-species: browni is found along the west coast, athalassos in the central U.S., and antifiarum along the east coast and the West Indies (Massev 198 1). The status of two subspecies described from Mexico, mexicanus from Sonora (Van Rossem and Hachisuka 1937) and stae-bleri from Chiapas (Brodkorb 1940) is uncertain. Least Terns have disjunct summer and wintering ranges, breeding in northeast, central, and southwest United States south to Baja California and Sonora in Mexico, and on some Caribbean islands. The east coast population (S. a. antillarum) comprises more than 7 5% ofall the individuals (Buckley and Buckley 1984; Clapp and Buckley 1984). The California Least Tern (S. a. browni) is less abundant; the largest concentration re-centlv recorded is in San Dieao. California (Massey 198 li. It is considered endangered; its populations began to decline early this century, mainly because of habitat loss, disturbance of nesting sites, and predation bv domestic and wild mammals (Ring 1981, Massey 198 1, Jehl 1984, Vermeer and Ranking 1984). California Least Terns breed from the San Francisco Bay in California southward to the tip of the Baja Cal-ifornia Peninsula and Sonora, Mexico (Russell and Lamm 1978, Massey 198 1, Mellink and Palacios 1993); early in the century a breeding colony was recorded in Oaxaca (Binford 1989). It winters along the coasts of western Mexico, south to northern South America (King 198 1, AOU 1983). A group of seventy-five wintering Least Terns was found in Colima in 1979; additionally, some banded Least Terns were found in the same area in 198 1, and this region is considered the northern limit of its wintering range (Massey 198 1). We report here the first recent tropical breeding record of Least Tern in Mexico, from the Cuixmala River in Jalisco, 150 km to the north of Boca de Pascuales, Colima, the northern limit of the wintering range (Mas-sey 1981). Aside from extending the recent breeding records in Mexico more than 1,000 km to the south, we report the only clutch size data for this subspecies from the tropics, and raise questions about its summer and wintering distribution range.
Aim: Understanding determinants of species' range size is paramount to explaining global ecologic... more Aim: Understanding determinants of species' range size is paramount to explaining global ecological patterns and estimating extinction risk of species. Here, we examined whether a sample of 536 snake species exhibits a latitudinal gradient of range size in support of Rapoport's rule, and determined predictors of range size from a set of environmental and biological factors. Location: Global. Methods: Based on a priori hypotheses about the effects of latitude, environmental and biological factors on species' range, we calculated mid-latitudes of species ranges, and collected data on environmental factors (altitude, temperature, precipitation , size and number of ecoregions occupied) and biological traits (body size, fe-cundity, habitat breadth and species age) to construct multivariate models of snake range size. We used a recently published dated consensus phylogeny to determine minimum adequate models of range size using phylogenetic generalized least squares models and establish correlations between range size and time since species' description. Results: Range size increased significantly with latitude, consistent with Rapoport's rule, especially across mid-and high latitudes in the Northern Hemisphere. Habitat breadth, body size and altitudinal range had a significant positive effect on range size, with minor negative effects on range size from mean altitude and reproductive output. Biological variables explained more variation in range size than environmental variables. Species' range size had a significant effect on species' description, with larger-ranged species having been described earlier. Main conclusions: Prediction of range size in lesser-known species such as snakes relies on a suite of factors. Species with restricted habitat breadth, small body size and at high altitudes a wider altitudinal range generally have smaller ranges, and are thus likely to have higher extinction risk. Our work illustrates that it is these species we are likely to under-report in extinction risk assessments. K E Y W O R D S extinction risk, habitat breadth, IUCN Red List, phylogeny, Rapoport's rule, reptiles
The distribution of amphibians is affected by abiotic and biotic factors, availability of resourc... more The distribution of amphibians is affected by abiotic and biotic factors, availability of resources and the characteristics of reproductive sites. In particular, reproductive activity of aquatic-breeding anurans that inhabit tropical dry areas is affected by rainfall, which determines the availability and quality of reproductive sites. In this study, we analyzed the spatial and temporal distribution of anurans with indirect development in a tropical dry forest in Western Mexico, during two rainy seasons (July 10-October 4, 2013, and June 26-September 26, 2014). We collected data on the occupancy and reproductive activity of 15 species in four temporary streams, and evaluated their relationship with precipitation, humidity and temperature. We determined richness, abundance and diversity of species in each stream; we also identified differences in the reproductive strategies and microhabitats used by the species. The most abundant species were: Tlalocohyla smithii and Exerodonta smaragdina, whereas the least abundant were Leptodactylus melanonotus and Incilius mazatlanen-sis. Species richness, abundance and reproductive activity peaked alongside the stream with the greatest number of breeding sites (e.g. pools). We found temporal segregation in the occupancy and reproductive activity of species in all streams which were mainly associated with precipitation. However, occupancy and reproductive activity of some species overlapped up to four weeks during part of the breeding season. Most species used specific substrates for particular reproductive activities (e.g. oviposition), but used a range of microhabitats (leaf-litter, water, rocks, branches, leaves, logs, etc.) for others (e.g. calling). We discuss these behavioral differences as factors that facilitate coexistence of species in this environment in the rainy season. Rev. Biol. Trop. 65 (3): 1082-1094. Epub 2017 September 01.
Supplementary Material. Classification of bird species from a Mexican wetland in a hierarchical s... more Supplementary Material. Classification of bird species from a Mexican wetland in a hierarchical system of foraging guilds (FG) nested within trophic guilds (TG). The following categories of trophic resources are classified as being of minor (Min), significant (Sig), and major (Maj)
We conducted a survey on chigger mites infesting amphibians at Los Tuxtlas Biosphere Reserve in S... more We conducted a survey on chigger mites infesting amphibians at Los Tuxtlas Biosphere Reserve in Southeast Mexico, where we collected 25 frogs of three species: Lithobates berlandieri (n = 5), L. brownorum (n = 3) and L. vaillanti (n = 17). A total of 916 mites belonging to Hannemania mexicana Hoffmann, 1965 were collected. It is the first record of H. mexicana in the state of Veracruz and in L. brownorum and L. vaillanti. The frog species with the highest level of infestation was L. berlandieri with a prevalence of 80%, a mean abundance of 56 mites per host, and a mean intensity of 70 mites per infested host. Additionally, to corroborate identification we compared specimens from the type series of H. mexicana and we found variation in some characters of taxonomic importance such as the number of setae on leg genu and the shape of the palpal claw.
Relative to the West Indies, the ecology and evolution of anoles inhabiting islands off Central a... more Relative to the West Indies, the ecology and evolution of anoles inhabiting islands off Central and South America have received little attention. The paucity of studies on continental islands has limited our ability to generalize and extend results based on the West Indian paradigm, as well as our understanding of the profound differences between the adaptive radiations of continental vs. Greater Antillean anoles. Here we compare the morphological, ecological, behavioural and genetic divergence between Anolis nebulosus populations inhabiting a small island in the Bay of Chamela, Mexico, and a nearby mainland forest. Notably, the two populations exhibit intra-sexual dimorphism with respect to head and limb sizes, the first such polymorphism documented for an Anolis species. We also compare the shape of island and mainland A. nebulosus with each other, the six West Indian ecomorphs and a hypothetical generalist species. Finally, we address the generalist convergence hypothesis for anoles on single species islands. We conclude that convergence on a generalist morphology is widespread among solitary anoles in the West Indies. We present data on a limited sample of solitary anoles with mainland ancestors that suggest a parallel convergence on a similar generalist morphology, probably due to similar adaptive landscapes shaped by selective forces common to small island environments.
Aim Evaluating the relative roles of biological traits and environmental factors that predispose ... more Aim Evaluating the relative roles of biological traits and environmental factors that predispose species to an elevated risk of extinction is of fundamental importance to macroecology. Identifying species that possess extinction-promoting traits allows targeted conservation action before precipitous declines occur. Such analyses have been carried out for several vertebrate groups, with the notable exception of reptiles. We identify traits correlating with high extinction risk in squamate reptiles, assess whether these differ with geography, taxonomy and threats, and make recommendations for future Red List assessments. Location Global. Methods We collected data on biological traits and environmental factors for a representative sample of 1139 species of squamate reptiles. We used phylogenetically controlled regression models to identify general correlates of extinction risk, threat-specific correlates of risk and realm-specific correlates of risk. We also assessed the relative importance of range size versus other factors through multiplicative bivariate models, partial regressions and variance partitioning. Results Range size was the most important predictor of extinction risk, reflecting the high frequency of reptiles assessed under range-based IUCN criteria. Habitat specialists occupying accessible ranges were at a greater risk of extinction: although these factors never contributed more than 10% to the variance in extinction risk, they showed significant interactions with range size. The predictive power of our global models ranged from 23% to 29%. The general overall pattern remained the same among geographical, taxonomic and threat-specific data subsets. Main conclusions Proactive conservation requires shortcuts to identify species at high risk of extinction. Regardless of location, squamate reptiles that are range-restricted habitat specialists living in areas highly accessible to humans are likely to become extinct first. Prioritizing species that exhibit such traits could forestall extinction. Integration of data sources on human pressures, such as accessibility of species ranges, may aid robust and time-efficient assessments of species extinction risk.
Amphibian populations are globally declining at an alarming rate, and infectious diseases are amo... more Amphibian populations are globally declining at an alarming rate, and infectious diseases are among the main causes of their decline. Two micro-parasites, the fungus Batrachochytrium dendrobatidis (Bd) and the virus Ranavirus (RV) have caused mass mortality of amphibians and population declines. Other, less understood epizootics are caused by macro-parasites, such as Trombiculoidea chiggers. Infection with chiggers can affect frog behavior and survival. Furthermore, synergistic effects of co-infection with both macro and micro-parasites may lead to higher morbidity. To better understand these potential synergies, we investigated the presence and co-infection by chiggers, Bd and RV in the endemic frog Tlalocohyla smithii (T. smithii). Co-infection of Bd, RV, and/or chiggers is expected in habitats that are suitable for their co-occurrence; and if infection with one parasite facilitates infection with the others. On the other hand, co-infection could decrease if these parasites were to differ in their micro-environmental requirements (i.e. niche apportionment). A total of 116 frogs of T. smithii were studied during 2014 and 2016 in three streams within the Chamela-Cuixmala Biosphere Reserve in Jalisco, Mexico. Our results show that 31% of the frogs were infected with Trombiculoidea chiggers (Hannemania sp. and Eutrombicula alfreddugesi); Hannemania prevalence increased with air temperature and decreased in sites with high canopies and with water pH values above 8.5 and below 6.7. Bd prevalence was 2.6%, RV prevalence was 0%, and none of the frogs infected with chiggers were co-infected with Bd. Together, this study suggests that chiggers do not facilitate infection with Bd, as these are apportioned in different micro-habitats. Nevertheless, the statistical power to assure this is low. We recommend further epidemiological monitoring of multiple parasites in different geographical locations in order to provide insight on the true hazards, risks and conservation options for amphibian populations.
The Least Tern (Sterna antillarum) is broadly distributed in the United States, with three well-d... more The Least Tern (Sterna antillarum) is broadly distributed in the United States, with three well-defined sub-species: browni is found along the west coast, athalassos in the central U.S., and antifiarum along the east coast and the West Indies (Massev 198 1). The status of two subspecies described from Mexico, mexicanus from Sonora (Van Rossem and Hachisuka 1937) and stae-bleri from Chiapas (Brodkorb 1940) is uncertain. Least Terns have disjunct summer and wintering ranges, breeding in northeast, central, and southwest United States south to Baja California and Sonora in Mexico, and on some Caribbean islands. The east coast population (S. a. antillarum) comprises more than 7 5% ofall the individuals (Buckley and Buckley 1984; Clapp and Buckley 1984). The California Least Tern (S. a. browni) is less abundant; the largest concentration re-centlv recorded is in San Dieao. California (Massey 198 li. It is considered endangered; its populations began to decline early this century, mainly because of habitat loss, disturbance of nesting sites, and predation bv domestic and wild mammals (Ring 1981, Massey 198 1, Jehl 1984, Vermeer and Ranking 1984). California Least Terns breed from the San Francisco Bay in California southward to the tip of the Baja Cal-ifornia Peninsula and Sonora, Mexico (Russell and Lamm 1978, Massey 198 1, Mellink and Palacios 1993); early in the century a breeding colony was recorded in Oaxaca (Binford 1989). It winters along the coasts of western Mexico, south to northern South America (King 198 1, AOU 1983). A group of seventy-five wintering Least Terns was found in Colima in 1979; additionally, some banded Least Terns were found in the same area in 198 1, and this region is considered the northern limit of its wintering range (Massey 198 1). We report here the first recent tropical breeding record of Least Tern in Mexico, from the Cuixmala River in Jalisco, 150 km to the north of Boca de Pascuales, Colima, the northern limit of the wintering range (Mas-sey 1981). Aside from extending the recent breeding records in Mexico more than 1,000 km to the south, we report the only clutch size data for this subspecies from the tropics, and raise questions about its summer and wintering distribution range.
Aim: Understanding determinants of species' range size is paramount to explaining global ecologic... more Aim: Understanding determinants of species' range size is paramount to explaining global ecological patterns and estimating extinction risk of species. Here, we examined whether a sample of 536 snake species exhibits a latitudinal gradient of range size in support of Rapoport's rule, and determined predictors of range size from a set of environmental and biological factors. Location: Global. Methods: Based on a priori hypotheses about the effects of latitude, environmental and biological factors on species' range, we calculated mid-latitudes of species ranges, and collected data on environmental factors (altitude, temperature, precipitation , size and number of ecoregions occupied) and biological traits (body size, fe-cundity, habitat breadth and species age) to construct multivariate models of snake range size. We used a recently published dated consensus phylogeny to determine minimum adequate models of range size using phylogenetic generalized least squares models and establish correlations between range size and time since species' description. Results: Range size increased significantly with latitude, consistent with Rapoport's rule, especially across mid-and high latitudes in the Northern Hemisphere. Habitat breadth, body size and altitudinal range had a significant positive effect on range size, with minor negative effects on range size from mean altitude and reproductive output. Biological variables explained more variation in range size than environmental variables. Species' range size had a significant effect on species' description, with larger-ranged species having been described earlier. Main conclusions: Prediction of range size in lesser-known species such as snakes relies on a suite of factors. Species with restricted habitat breadth, small body size and at high altitudes a wider altitudinal range generally have smaller ranges, and are thus likely to have higher extinction risk. Our work illustrates that it is these species we are likely to under-report in extinction risk assessments. K E Y W O R D S extinction risk, habitat breadth, IUCN Red List, phylogeny, Rapoport's rule, reptiles
The distribution of amphibians is affected by abiotic and biotic factors, availability of resourc... more The distribution of amphibians is affected by abiotic and biotic factors, availability of resources and the characteristics of reproductive sites. In particular, reproductive activity of aquatic-breeding anurans that inhabit tropical dry areas is affected by rainfall, which determines the availability and quality of reproductive sites. In this study, we analyzed the spatial and temporal distribution of anurans with indirect development in a tropical dry forest in Western Mexico, during two rainy seasons (July 10-October 4, 2013, and June 26-September 26, 2014). We collected data on the occupancy and reproductive activity of 15 species in four temporary streams, and evaluated their relationship with precipitation, humidity and temperature. We determined richness, abundance and diversity of species in each stream; we also identified differences in the reproductive strategies and microhabitats used by the species. The most abundant species were: Tlalocohyla smithii and Exerodonta smaragdina, whereas the least abundant were Leptodactylus melanonotus and Incilius mazatlanen-sis. Species richness, abundance and reproductive activity peaked alongside the stream with the greatest number of breeding sites (e.g. pools). We found temporal segregation in the occupancy and reproductive activity of species in all streams which were mainly associated with precipitation. However, occupancy and reproductive activity of some species overlapped up to four weeks during part of the breeding season. Most species used specific substrates for particular reproductive activities (e.g. oviposition), but used a range of microhabitats (leaf-litter, water, rocks, branches, leaves, logs, etc.) for others (e.g. calling). We discuss these behavioral differences as factors that facilitate coexistence of species in this environment in the rainy season. Rev. Biol. Trop. 65 (3): 1082-1094. Epub 2017 September 01.
Supplementary Material. Classification of bird species from a Mexican wetland in a hierarchical s... more Supplementary Material. Classification of bird species from a Mexican wetland in a hierarchical system of foraging guilds (FG) nested within trophic guilds (TG). The following categories of trophic resources are classified as being of minor (Min), significant (Sig), and major (Maj)
We conducted a survey on chigger mites infesting amphibians at Los Tuxtlas Biosphere Reserve in S... more We conducted a survey on chigger mites infesting amphibians at Los Tuxtlas Biosphere Reserve in Southeast Mexico, where we collected 25 frogs of three species: Lithobates berlandieri (n = 5), L. brownorum (n = 3) and L. vaillanti (n = 17). A total of 916 mites belonging to Hannemania mexicana Hoffmann, 1965 were collected. It is the first record of H. mexicana in the state of Veracruz and in L. brownorum and L. vaillanti. The frog species with the highest level of infestation was L. berlandieri with a prevalence of 80%, a mean abundance of 56 mites per host, and a mean intensity of 70 mites per infested host. Additionally, to corroborate identification we compared specimens from the type series of H. mexicana and we found variation in some characters of taxonomic importance such as the number of setae on leg genu and the shape of the palpal claw.
Relative to the West Indies, the ecology and evolution of anoles inhabiting islands off Central a... more Relative to the West Indies, the ecology and evolution of anoles inhabiting islands off Central and South America have received little attention. The paucity of studies on continental islands has limited our ability to generalize and extend results based on the West Indian paradigm, as well as our understanding of the profound differences between the adaptive radiations of continental vs. Greater Antillean anoles. Here we compare the morphological, ecological, behavioural and genetic divergence between Anolis nebulosus populations inhabiting a small island in the Bay of Chamela, Mexico, and a nearby mainland forest. Notably, the two populations exhibit intra-sexual dimorphism with respect to head and limb sizes, the first such polymorphism documented for an Anolis species. We also compare the shape of island and mainland A. nebulosus with each other, the six West Indian ecomorphs and a hypothetical generalist species. Finally, we address the generalist convergence hypothesis for anoles on single species islands. We conclude that convergence on a generalist morphology is widespread among solitary anoles in the West Indies. We present data on a limited sample of solitary anoles with mainland ancestors that suggest a parallel convergence on a similar generalist morphology, probably due to similar adaptive landscapes shaped by selective forces common to small island environments.
Aim Evaluating the relative roles of biological traits and environmental factors that predispose ... more Aim Evaluating the relative roles of biological traits and environmental factors that predispose species to an elevated risk of extinction is of fundamental importance to macroecology. Identifying species that possess extinction-promoting traits allows targeted conservation action before precipitous declines occur. Such analyses have been carried out for several vertebrate groups, with the notable exception of reptiles. We identify traits correlating with high extinction risk in squamate reptiles, assess whether these differ with geography, taxonomy and threats, and make recommendations for future Red List assessments. Location Global. Methods We collected data on biological traits and environmental factors for a representative sample of 1139 species of squamate reptiles. We used phylogenetically controlled regression models to identify general correlates of extinction risk, threat-specific correlates of risk and realm-specific correlates of risk. We also assessed the relative importance of range size versus other factors through multiplicative bivariate models, partial regressions and variance partitioning. Results Range size was the most important predictor of extinction risk, reflecting the high frequency of reptiles assessed under range-based IUCN criteria. Habitat specialists occupying accessible ranges were at a greater risk of extinction: although these factors never contributed more than 10% to the variance in extinction risk, they showed significant interactions with range size. The predictive power of our global models ranged from 23% to 29%. The general overall pattern remained the same among geographical, taxonomic and threat-specific data subsets. Main conclusions Proactive conservation requires shortcuts to identify species at high risk of extinction. Regardless of location, squamate reptiles that are range-restricted habitat specialists living in areas highly accessible to humans are likely to become extinct first. Prioritizing species that exhibit such traits could forestall extinction. Integration of data sources on human pressures, such as accessibility of species ranges, may aid robust and time-efficient assessments of species extinction risk.
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