4.2 TNR limits
Sea snakes demonstrate a greater consistency in their upper thermal
limits compared to their lower thermal limits, according to our research
findings. This aligns with previous studies on some terrestrial (Araújo
et al. 2013; Sunday et al. 2011, 2012) and marine ectothermic species
(Grady et al. 2019; Nishizaki et al. 2015; Stuart-Smith et al. 2017).
The results imply that cold tolerance evolves more quickly than heat
tolerance in both endothermic and ectothermic organisms (Bennett et al.
2018). Sea snakes may have developed greater plasticity in their lower
thermal limits through an evolutionary process (Gunderson and Stillman
2015; Verberk et al. 2018), resulting in less variation in their upper
thermal limits. However, if sea temperatures continue to rise due to
climate change, the reduced variability in upper thermal limits could
have significant consequences for sea snakes (Araújo et al. 2013;
Udyawer et al. 2020).
Marine ectotherms have a low physiological acclimatization rate, making
them particularly susceptible to the effects of climate change (Deutsch
et al. 2008; Sunday et al. 2011). Previous studies have indicated that
sea snakes exist near their upper thermal limits (Heatwole et al. 2012),
and that tropical species generally do not surpass the maximum
temperatures of the organisms that have been collected (Deutsch et al.
2008; Huey et al. 2009). Although our study observed this pattern at the
lineage level, we obtained mixed results at the subfamily and genus
level, potentially owing to our limited sample size. Other factors,
including biotic interactions, geographic barriers, and dispersal
processes, may restrict species distribution and impact the capacity to
measure complete thermal niches (Bennett et al. 2018; Sunday et al.
2011, 2012).
The consequences of the observed asymmetric realized thermal limits for
sea snakes’ physiological performance and their ecological interactions
with other species in their habitat are significant. Sea snakes are
critical predators in their marine ecosystems, and alterations in their
distribution or abundance could have cascading effects on the food webs
they inhabit (Lukoschek et al. 2013). Thus, the observed thermal limits
of sea snakes have implications not only for their own survival but also
for the health and functioning of marine ecosystems.
To address the conservation implications of our findings, it is crucial
to consider the potential impact of climate change on sea snakes and the
measures needed to protect them. Management and conservation efforts
must recognize the susceptibility of many marine species, including sea
snakes, to climate change (Somaweera et al. 2021). Our research
highlights the importance of conservation efforts that consider the
potential vulnerability of sea snakes to changes in sea temperature,
including identifying areas that provide thermal refugia for sea snakes,
monitoring populations for changes in distribution or abundance, and
implementing adaptive management strategies that can respond to changing
conditions (Udyawer et al. 2020).
While our study offers valuable insights into the realized thermal
limits of sea snakes, there are limitations and gaps in knowledge that
future research could address. For example, our sample size for some
subfamilies and genera was relatively small, which may have affected our
results. Increasing the sample size may enhance the robustness of our
findings. Moreover, future research could explore the potential for sea
snakes to acclimate or adapt to warming temperatures and investigate the
mechanisms underlying the observed pattern of asymmetric realized
thermal limits. Integrating physiological and genetic data could provide
a more comprehensive understanding of the thermal ecology of sea snakes
and their ability to adapt in the face of climate change.