Post-delisting genetic monitoring reveals population subdivision along river and reservoir localities of the endemic Concho water snake (Nerodia harteri paucimaculata)

Becker

Yates

et al. 2022

Sci Rep

The ascomycete fungus Ophidiomyces ophiodiicola (Oo) is the causative agent of ophidiomycosis (Snake Fungal Disease), which has been detected globally. However, surveillance efforts in the central U.S., specifically Texas, have been minimal. The threatened and rare Brazos water snake (Nerodia harteri harteri) is one of the most range restricted snakes in the U.S. and is sympatric with two wide-ranging congeners, Nerodiaerythrogaster transversa and Nerodiarhombifer, in north central Texas; thus, providing an opportunity to test comparative host–pathogen associations in this system. To accomplish this, we surveyed a portion of the Brazos river drainage (~ 400 river km) over 29 months and tested 150 Nerodia individuals for the presence of Oo via quantitative PCR and recorded any potential signs of Oo infection. We found Oo was distributed across the entire range of N. h. harteri, Oo prevalence was 46% overall, and there was a significant association between Oo occurrence and signs of infection in our sample. Models indicated adults had a higher probability of Oo infection than juveniles and subadults, and adult N. h. harteri had a higher probability of infection than adult N. rhombifer but not higher than adult N. e. transversa. High Oo prevalence estimates (94.4%) in adult N. h. harteri has implications for their conservation and management owing to their patchy distribution, comparatively low genetic diversity, and threats from anthropogenic habitat modification.

Section: Discussionmentioning

confidence: 97%

Comparative host–pathogen associations of Snake Fungal Disease in sympatric species of water snakes (Nerodia)

Becker

Yates

et al. 2022

Sci Rep

“…For instance, spatial ecology studies have shown N. h. paucimaculata can exhibit high site fidelity and are unlikely to move more than 1 km unless driven by stochastic factors such as variable water flow 33 . It is likely that N. h. harteri movement among sites is likewise rare, given their low detection probability, the barriers to movement within the Brazos River (i.e., dams or unsuitable habitat), and evidence of genetic population structure in N. h. paucimaculata , which shares many ecological attributes with N. h. harteri 31,57 .…”

Section: Discussionmentioning

confidence: 99%

“…Combined with a moderately high prevalence of Oo (47.4% overall, Table 1), this finding highlights the need for continued Oo surveillance and renewed conservation action planning. Previous studies have shown that both subspecies of N. harteri have low genetic diversity, and N. h. paucimaculata populations exhibit bottleneck signatures 31,57 . The application of additional sampling and genetic markers are needed, however, to facilitate robust tests for population contractions and their timing in N. harteri 31,57 .…”

Section: Conservation Implicationsmentioning

confidence: 97%

“…Previous studies have shown that both subspecies of N. harteri have low genetic diversity, and N. h. paucimaculata populations exhibit bottleneck signatures 31,57 . The application of additional sampling and genetic markers are needed, however, to facilitate robust tests for population contractions and their timing in N. harteri 31,57 . For instance, spatial ecology studies have shown N. h. paucimaculata can exhibit high site fidelity and are unlikely to move more than 1 km unless driven by stochastic factors such as variable water flow 33 .…”

Section: Conservation Implicationsmentioning

confidence: 97%

“…harteri 31,57 . For instance, spatial ecology studies have shown N. h. paucimaculata can exhibit high site fidelity and are unlikely to move more than 1 km unless driven by stochastic factors such as variable water flow 33 .…”

Section: Conservation Implicationsmentioning

confidence: 99%

See 2 more Smart Citations

Comparative host-pathogen dynamics of Snake Fungal Disease in sympatric species of water snakes (Nerodia)

Becker

Yates

et al. 2022

Preprint

The ascomycete fungus Ophidiomyces ophiodiicola (Oo) is the causative agent of ophidiomycosis (Snake Fungal Disease), which has been detected globally. However, surveillance efforts in the central U.S., specifically Texas, have been minimal. The threatened and rare Brazos water snake (Nerodia harteri harteri) is one of the most range restricted snakes in the U.S. and is sympatric with two wide-ranging congeners, N. erythrogaster transversa and N. rhombifer, in north central Texas; thus, providing an opportunity to test comparative host-pathogen dynamics in this system. To accomplish this, we surveyed a portion of the Brazos river drainage (~400 river km) over 29 months and tested 150 Nerodia spp. for the presence of Oo via quantitative PCR and recorded any potential signs of Oo infection. We found Oo was distributed across the entire range of N. h. harteri, Oo prevalence was 46 % overall, and there was a significant association between Oo occurrence and signs of infection in our sample. Models indicated adults had a higher probability of Oo infection than juveniles and subadults, and adult N. h. harteri had a higher probability of infection than adult N. rhombifer but not higher than adult N. e. transversa. High Oo prevalence estimates (94.4%) in adult N. h. harteri has implications for their conservation and management owing to their patchy distribution, comparatively low genetic diversity, and threats from anthropogenic habitat modification.

Leveraging preserved specimens of Nerodia to infer the spatiotemporal dynamics of Ophidiomyces ophidiicola via quantitative polymerase chain reaction

Moretta‐Urdiales

Nordmeyer

et al. 2023

Ecology and Evolution

Ophidiomyces ophidiicola (Oo) is a fungal pathogen and the causative agent of ophidiomycosis that has affected multiple snake taxa across the United States, Europe, and Asia. Ophidiomycosis has often been referred to as an emerging infectious disease (EID); however, its status as an EID has recently come under debate. Oo infections have been confirmed in wild snake populations in Texas; however, it is unknown if the pathogen is novel (i.e., invasive) or endemic to the state. To address this knowledge gap, we conducted surveys for Oo among preserved Nerodia deposited at three university museums in Texas. First, we visually assessed snakes for signs of infection (SOI), and if SOI were present, we sampled the affected area. We then used quantitative polymerase chain reaction to diagnose the presence of Oo DNA on areas with SOI and used these data to evaluate spatiotemporal patterns of Oo prevalence. We also tested for significant spatial clusters of Oo infenction using a Bernoulli probability model as implemented in the program SatScan. We found that the proportion of snakes exhibiting SOI was constant over time while the prevalence of Oo DNA among those SOI increased across space and time. Within these data, we detected an incidence pattern consistent with an introduction and then spread. We detected six spatial clusters of Oo infection, although only one was significant. Our results support the hypothesis that Oo is an emerging, novel pathogen to Texas snakes. These data narrow the knowledge gap regarding the history of Oo infections in Texas and establish a historical record of confirmed Oo detections in several counties across the state. Thus, our results will guide future research to those areas with evidence of past Oo infections but lacking confirmation in contemporary hosts.