4.1 Environmental variables
Our study confirms the importance of environmental variables in shaping
the distribution of sea snakes, which is consistent with previous
studies (Bessesen et al. 2023; Udyawer et al. 2014). Environmental
variables play a crucial role in determining the habitat suitability and
area of occupancy of marine species, including sea snakes, and
prioritizing search efforts based on habitat suitability models can help
locate previously unknown populations of endangered marine reptiles
(Udyawer et al. 2020). This aligns with our findings and emphasizes the
importance of our research in generating crucial information that could
guide future conservation and management strategies for protecting a
highly vulnerable and ecologically important group, which is sea snakes.
Our findings are consistent with a meta-analysis on the importance of
variables used in MaxEnt species distribution models, which found that
the most important factors in determining the distribution of marine
organisms were temperature, bathymetry, and precipitation (Bradie and
Leung 2017). Additionally, our study highlights the importance of
nutrient availability in shaping the distribution of marine species.
Those environmental variables were not important in the meta-analysis.
The study by Bosch et al. (2018) found that temperature, bathymetry, and
distance to shore were the most important predictors for marine species
distribution, while salinity and nutrients had less influence. Although
our study’s results on the importance of salinity and nutrients in
determining sea snakes’ distribution appear to conflict with previous
analysis, it is worth noting that our study specifically focused on sea
snakes, which may have different environmental preferences than other
marine species. Our study’s results on the importance of phosphates,
salinity, and temperature in determining the habitat suitability and
area of occupancy of sea snakes are consistent with the findings of
Bessesen et al. (2023) on H. platurus and Udyawer et al. (2014)
on sea snakes in the Great Barrier Reef Marine Park.
The combination of climate and nutrient variables are known to have
implications for the morphology, diving behavior, feeding habits of sea
snakes and also coral reefs health (Brischoux et al. 2012; Gherghel et
al. 2018; Heatwole et al. 2012; Sherratt et al. 2018; Veron 2000, 2008).
Temperature, along with salinity, plays a crucial role in the physiology
of sea snakes, affecting their metabolic rates, oxygen uptake, and blood
chemistry (Heatwole et al. 2012; Udyawer et al. 2016). Studies have also
demonstrated that metabolic thermal sensitivity optimizes sea krait
amphibious physiology, enabling them to tolerate fluctuations in
temperature (Dabruzzi et al. 2012; Heatwole et al. 2012). Furthermore,
trophic specialization drives morphological evolution in sea snakes,
while the dependence of dive behaviors and metabolism on temperature has
also been observed (Dabruzzi et al. 2012; Sherratt et al. 2018; Udyawer
et al. 2016). However, plasticity in thermal tolerance has limited
potential to buffer ectotherms from global warming, which may lead to
mosaic patterns of thermal stress with implications for climate change
(Gunderson and Stillman 2015; Helmuth et al. 2006). Phosphates play a
significant role in the distribution of sea snakes as they are essential
for the growth and development of the coral reefs where sea snakes are
commonly found (Veron 2000). Although the importance of nitrogen and
silicates in the distribution of sea snakes is less clear, they are
likely to play a role in the availability of prey species that sea
snakes feed on (Gherghel et al. 2018). Nitrogen is an essential nutrient
for many marine organisms, and its availability can influence the
abundance and distribution of prey species (Brischoux et al. 2012).
Silicates are important in the growth of diatoms, which are a primary
food source for many marine organisms, including some species of sea
snakes (Sherratt et al. 2018).
The sea snakes’ distribution may have influenced their diet and feeding
behavior, as species that occur in areas with higher nutrient
availability may have evolved to specialize on prey that require higher
energy requirements, such as fish, while species occurring in areas with
lower nutrient availability may have evolved to specialize on prey that
require less energy, such as crustaceans (Gherghel et al. 2018; Sherratt
et al. 2018).
Our study utilized correlative models to determine the relationships
between sea snakes and environmental variables, but caution must be
exercised in interpreting the results since correlative models cannot
establish causality. Some correlations may reflect direct effects of
environmental variables, while others may represent indirect
relationships. We used MaxEnt, which can handle collinearity among
explanatory variables; however, collinearity may still pose challenges
when estimating the importance of explanatory variables (Smith and
Santos 2020). The programmers of MaxEnt incorporated two different
metrics (PC and PI) to evaluate the contribution of predictors to the
model (Phillips 2011), although there is no consensus in the literature
on which is more informative. Most studies use the PC, possibly because
it appears first in the algorithm’s results. Halvorsen (2013) concluded
that the PC is most informative, whereas (Searcy and Shaffer 2016)
suggested that the PI is better for describing the biological properties
of species. Our study provides insights into the environmental factors
important for the distribution of sea snakes, but further research is
necessary to establish causal relationships between these factors and
the distribution of sea snakes, as well as to gain a better
understanding of their ecology and behavior.
In summary, our results on the relative importance of environmental
variables in shaping the distribution and potentially the abundance of
sea snakes, are consistent with previous research on marine organisms
and provide a valuable framework for developing effective conservation
management plans for sea snakes.