scholarly journals Microgeographic variation in body condition of three Mexican garter snakes in central Mexico

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6601 ◽  
Author(s):  
Erika Valencia-Flores ◽  
Crystian S. Venegas-Barrera ◽  
Victor Fajardo ◽  
Javier Manjarrez

BackgroundGeographic variation in body size and condition can reveal differential local adaptation to resource availability or climatic factors. Body size and condition are related to fitness in garter snakes (Thamnophis), thus good body condition may increase survival, fecundity in females, and mating success in males. Phylogenetically related species in sympatry are predicted to exhibit similar body condition when they experience similar environmental conditions. We focused on interspecific and geographical variation in body size and condition in three sympatric Mexican garter snakes from the highlands of Central Mexico.MethodsWe assessed SVL, mass, and body condition (obtained from Major axis linear regression of ln-transformed body mass on ln-transformed SVL) in adults and juveniles of both sexes ofThamnophis eques,T. melanogaster, andT. scalarissampled at different locations and ranges from 3–11 years over a 20-year period.ResultsWe provide a heterogeneous pattern of sexual and ontogenic reproductive status variations of body size and condition among local populations. Each garter snake species shows locations with good and poor body condition; juvenile snakes show similar body condition between populations, adults show varying body condition between populations, and adults also show sex differences in body condition. We discuss variations in body condition as possibly related to the snakes’ life cycle differences.

2018 ◽  
Author(s):  
Erika Valencia-Flores ◽  
Crystian S Venegas-Barrera ◽  
Victor Fajardo ◽  
Javier Manjarrez

Background. Geographic variation in body size and condition can reveal differential local adaptation to resource availability or climatic factors. Body size and condition are related to fitness in garter snakes (Thamnophis), thus good body condition may increase survival, fecundity in females, and mating success in males. Sympatric species are predicted to exhibit similar body condition when they experience similar environmental conditions. We focused on interspecific and geographical variation in body size and condition in three sympatric Mexican garter snakes from the highlands of Central Mexico. Methods. We assessed SVL, mass, and body condition (obtained from Major axis linear regression of ln-transformed body mass on ln-transformed SVL) in adults and juveniles of both sexes of Thamnophis eques, T. melanogaster, and T. scalaris sampled at different locations and over a 20-year period. Results. We provide a heterogeneous pattern of sexual and ontogenic reproductive status variations of body size and condition among local populations. Each garter snake species shows locations with good and poor body condition; juvenile snakes show similar body condition between populations, adults show varying body condition between populations, and adults also show sexual differences in body condition. We discuss variations in body condition as possibly related to the snakes’ life cycle differences.


2018 ◽  
Author(s):  
Erika Valencia-Flores ◽  
Crystian S Venegas-Barrera ◽  
Victor Fajardo ◽  
Javier Manjarrez

Background. Geographic variation in body size and condition can reveal differential local adaptation to resource availability or climatic factors. Body size and condition are related to fitness in garter snakes (Thamnophis), thus good body condition may increase survival, fecundity in females, and mating success in males. Sympatric species are predicted to exhibit similar body condition when they experience similar environmental conditions. We focused on interspecific and geographical variation in body size and condition in three sympatric Mexican garter snakes from the highlands of Central Mexico. Methods. We assessed SVL, mass, and body condition (obtained from Major axis linear regression of ln-transformed body mass on ln-transformed SVL) in adults and juveniles of both sexes of Thamnophis eques, T. melanogaster, and T. scalaris sampled at different locations and over a 20-year period. Results. We provide a heterogeneous pattern of sexual and ontogenic reproductive status variations of body size and condition among local populations. Each garter snake species shows locations with good and poor body condition; juvenile snakes show similar body condition between populations, adults show varying body condition between populations, and adults also show sexual differences in body condition. We discuss variations in body condition as possibly related to the snakes’ life cycle differences.


2011 ◽  
Vol 32 (3) ◽  
pp. 424-427 ◽  
Author(s):  
Karen Elgee ◽  
Gabriel Blouin-Demers

AbstractWe investigated sexual size dimorphism and trophic morphology dimorphism in Eastern Garter Snakes (Thamnophis sirtalis) to test predictions derived from the reproductive role hypothesis. Our first objective was to examine whether structures involved in feeding (head and jaws) are more divergent than body size. Female T. sirtalis were larger than males and had proportionally larger heads. Our second objective was to look for an advantage of large head size by examining the relationship between body condition and head size. Body condition was positively correlated with relative head size in T. sirtalis for both sexes, in agreement with the reproductive role hypothesis.


2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Maggie M. Hantak ◽  
Bryan S. McLean ◽  
Daijiang Li ◽  
Robert P. Guralnick

AbstractAnthropogenically-driven climate warming is a hypothesized driver of animal body size reductions. Less understood are effects of other human-caused disturbances on body size, such as urbanization. We compiled 140,499 body size records of over 100 North American mammals to test how climate and human population density, a proxy for urbanization, and their interactions with species traits, impact body size. We tested three hypotheses of body size variation across urbanization gradients: urban heat island effects, habitat fragmentation, and resource availability. Our results demonstrate that both urbanization and temperature influence mammalian body size variation, most often leading to larger individuals, thus supporting the resource availability hypothesis. In addition, life history and other ecological factors play a critical role in mediating the effects of climate and urbanization on body size. Larger mammals and species that utilize thermal buffering are more sensitive to warmer temperatures, while flexibility in activity time appears to be advantageous in urbanized areas. This work highlights the value of using digitized, natural history data to track how human disturbance drives morphological variation.


2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Lidya Gebresilassie ◽  
Berihun Afera Tadele

Background.Haemonchosiscaused byHaemonchus contortusis a predominant, highly pathogenic, and economically important disease of sheep and goats.Objective. Assessing the prevalence ofHaemonchusparasite and its associated risk factors in sheep slaughtered at different restaurants of Wukro.Methods. Cross-sectional study using random sampling from November 2013 to April 2014 in a total of 384 sheep was conducted and SPSS version 20 software using descriptive statistics was used for data analysis andP<0.05was considered significant.Result. The overall prevalence ofHaemonchus contortuswas 40.9% (n=157). The prevalence in medium body condition 27.3% (n=105) varies significantly from that of good body condition 13.5% (n=52) (P<0.05). Moreover, there was significant variation (P<0.05) in the prevalence in young and adult sheep with rates of 21.9% (n=84) and 19% (n=73), respectively. At the same time, there is significant variation (P<0.05) in male and female sheep with prevalence of 29.7% (n=114) and 11.2% (n=43), respectively. The prevalence of 25.3% (n=97) in sheep that originated from Negash compared to Wukro and Agulae showed no significant variation (P>0.05).Conclusion. The current finding revealed that significant numbers of sheep were affected by the parasites. Hence strategic deworming with good husbandry practice should be implemented.


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