How Lizards Evolve Together in Hawaii

Greg Howard
19th April, 2024

How Lizards Evolve Together in Hawaii

Key Findings

  • In O‘ahu, three lizard species showed changes in body size and limb length over time
  • Male A. sagrei, female A. carolinensis, and male P. laticauda lizards increased in body size
  • Female A. carolinensis lizards also developed longer hindlimbs, suggesting adaptation
Understanding how species adapt and change during the process of invasion can provide insights into the mechanisms of evolution and species interactions. A recent study by researchers from Valdosta State University[1] has shed light on this by examining the morphological changes in three lizard species that have invaded the island of O‘ahu. These species, which include Anolis carolinensis, A. sagrei, and Phelsuma laticauda, have overlapping ecological niches, meaning they compete for similar resources in their environment. The study focused on three specific traits: body size, measured as snout-vent length (SVL), and the lengths of forelimbs and hindlimbs relative to SVL. These traits are important for a lizard's mobility and ability to capture prey, escape predators, and compete for mates. By analyzing specimens collected over three decades, both from museum collections and recent fieldwork, the researchers could track how these traits have changed over time. The findings revealed that the lizards have undergone species-specific and sex-specific changes. For instance, male A. sagrei, female A. carolinensis, and male P. laticauda have all increased in body size (SVL). Additionally, female A. carolinensis showed an increase in relative hindlimb length. These changes suggest that the invasion process may be driving morphological adaptations, potentially due to the competition among these species. This study builds on earlier research that has explored how organisms at the forefront of an invasion, like the cane toad in Australia[2], can develop traits that give them an advantage in new territories. The cane toads at the invasion front exhibited traits such as higher feeding rates and better body condition, which may have been selected for due to factors like higher prey availability and lower pathogen levels. The current study extends this understanding by showing that even within a shared environment, different species and sexes can evolve distinct morphological traits, possibly in response to the unique pressures they face. Moreover, the study complements research on genetic variation and selection in species such as the brown anole lizard[3]. In that study, researchers found that a polymorphism in female dorsal patterns was maintained by temporal variation in selection, which alternated the relative fitness of different morphs across years. The recent study does not delve into genetic mechanisms but does highlight that phenotypic change can be a nuanced and dynamic process, affected by a variety of selective pressures. The concept of local adaptation and the role of phenotypic plasticity, as discussed in a perspective paper[4], is also relevant here. The current study illustrates how phenotypic changes can be indicative of ecological shifts, possibly as a result of local adaptation. While the study did not use a common garden experiment or genome-wide association studies as suggested in[4], it does provide a foundation for future research that could integrate these methods to further investigate the genetic basis of the observed morphological changes. In conclusion, the study from Valdosta State University highlights the importance of long-term, integrative research using both museum and field data to understand how species adapt morphologically in response to invasion. The species- and sex-specific changes observed in the lizards of O‘ahu emphasize that even within a group of co-invading species, individual and interactive evolutionary trajectories can be complex. This research not only contributes to our knowledge of invasion biology but also poses new questions about the processes driving these changes, which could be explored through the integration of genomic data and controlled experiments in the future.



Main Study

1) Analysis of Morphological Change during a Co-invading Assemblage of Lizards in the Hawaiian Islands

Published 17th April, 2024

Related Studies

2) The early toad gets the worm: cane toads at an invasion front benefit from higher prey availability.

3) Geographic variation, frequency-dependent selection, and the maintenance of a female-limited polymorphism.

4) Common garden experiments in the genomic era: new perspectives and opportunities.

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