Biology subjects

Debrot, A. O.

Publications and source records attributed to Debrot, A. O..

4 recordsLinked to original sources

bioRxiv2025

Larger hybrid clutch size could drive regional displacement of native Iguana populations across the Lesser Antilles

Native Iguana populations across the Caribbean Lesser Antilles are being replaced by non-native green iguanas (NNGI) once these establish themselves, leading to eventual extinction. Despite this knowledge, and much effort towards NNGI removal and prevention of incursions, the underlying mechanisms of the observed genetic swamping are poorly understood. Previous studies show that larger clutch size is a key reproductive trait of mainland as opposed to insular lizard populations. Higher clutch size in NNGI and their progeny could be a driver in the genetic swamping of insular Iguana populations. We collected data on snout-vent length, tail length, clutch size and genetics opportunistically during an eradication program of hybrid and NNGIs on the island of Saba, home to a native Iguana Iguana population. Data of native and hybrid iguanas from Saba were combined with similar published data from native insular and mainland Iguana populations. Generalized linear modeling revealed that climatic variables could not explain differences in clutch size, in contrast to genetic origins. Our preliminary results show that hybrid iguanas lay significantly more eggs (~40%) than similar-sized native Saba iguanas. Therefore, we suggest that higher hybrid clutch size may be a contributing factor hastening the genetic swamping and declines in native Iguana populations across the Lesser Antilles. Further study is needed to clarify and better understand the drivers of the rapid genetic swamping and loss of Antillean iguana diversity, which should also focus on Iguana delicatissima and utilize genomic approaches to pinpoint genes under selection.

ecology↗

bioRxiv2025

A genomic perspective on the origins, evolution and adaptation of Galapagos iguanas

Island taxa provide opportunities to explore the genomic basis of species diversification and trait evolution arising from adaptation to new environmental conditions and ecological niches. Here we generate the first genomic sequences for the four endemic Galapagos iguana species to reconstruct their evolutionary history and to identify genes which may contribute to their unique adaptations. We show that the marine (Amblyrhynchus) and land (Conolophus) lineages evolved in situ on now submerged islands, following a single colonisation event 9 - 12.4 million years ago. Genomic selection scans identified genes linked to traits potentially facilitating adaptation to the Galapagos environment, including specialised pigmentation phenotypes (e.g. ASIP, BCO2 and KITLG), DNA damage and UV irradiation inflammation responses (e.g. MAPK14 and BRAF), which may contribute to increased resilience to elevated UV exposure at equatorial latitudes. A shift from eumelanin (dark) to pheomelanin (yellow-orange) dominated colouration in Conolophus species may be attributable to fixed substitutions in the MC1R gene that influence protein structure and interactions, with the depigmented skin phenotype of the pink iguana additionally linked to positive selection in regulators of MITF activity, melanosome transport and dermal vasculature unique to that lineage. Further genes with signatures of positive selection in marine iguanas have putative functions including hypoxia response, that may be associated with their transition to underwater foraging (e.g. HBA, HMOX2, HIF), as well as their unique ability to repeatedly shrink and grow in body size through tissue and bone remodelling (e.g. AREG, BMP2, CPNE7). Genome-wide patterns of genetic diversity indicate recent inbreeding coincident with the timing of human settlement. Our study provides insights into the origins and diversification of the iguanas and the molecular basis of adaptation to life in the Galapagos, facilitating future conservation genomic management of threatened iguanid populations.

evolutionary biology↗

bioRxiv2024

Morphometrics as a conservation tool for rapid in-situ distinction of native and introduced iguanas: comparing Iguana delicatissima and Iguana iguana

Invasive alien species severely impact native and endemic species, disproportionately affecting insular species, and this is especially true for Caribbean reptiles. The Lesser Antillean iguana (Iguana delicatissima) experienced a drastic range decline strongly driven by hybridization with non-native green iguanas (NNGI, Iguana iguana species complex). With numerous NNGI populations within the Lesser Antilles, it is a matter of time before these arrive on the last I. delicatisisma inhabited islands, whereupon rapid in-situ identification of non-native and hybrid animals is essential. However, only a few scale and coloration characters allow in-situ identification of NNGI, which are compromised by introgression. Here we assessed the differentiating power of an additional 20 scale and length-dependent characteristics between the I. delicatissima population on St. Eustatius and the established NNGI population on St. Maarten, the main source of arriving stowaway iguanas on St. Eustatius. We identified 14 length-dependent characteristics that significantly differ between I. delicatissima and NNGIs, with multi-variate analysis showing clear morphospace separation and high assignment accuracy of predictive models (>91%). Additionally, the number of femorals and supra digital scales significantly differs between these iguanas. Morphospace knowledge of St. Eustatius I. delicatissima now allows rapid identification of any divergent iguanas using easy to obtain measurements and meristics. Given intraspecific variation in I. delicatissima and green iguanas, we recommend that these characteristics are assessed and validated for other populations, including hybrid individuals. Our work demonstrates the urgent need to invest in baseline morphometric datasets to aid rapid in-situ conservation efforts once NNGI arrive and start to hybridize with I. delicatissima.

zoology↗

bioRxiv2022

Population estimate, natural history and conservation of the melanistic Iguana iguana population on Saba, Caribbean Netherlands

Intraspecific diversity is among the most important biological variables, although still poorly understood for most species. Iguana iguana is a Neotropical lizard known from Central and South America, including from numerous Caribbean islands. Despite the presence of native melanistic I. iguana populations in the Lesser Antilles, these have received surprisingly little research attention. Here we assessed population size, distribution, degree of melanism, and additional morphological and natural history characteristics for the melanistic iguanas of Saba, Caribbean Netherlands based on a one-month fieldwork visit. Using Distance sampling from a 38-transect dataset we estimate the population size at 8233 {+/-}2205 iguanas. Iguanas mainly occurred on the southern and eastern sides of the island, between 180-390 m (max altitude 530 m), with highest densities both in residential and certain natural areas. Historically, iguanas were relatively more common at higher altitudes, probably due to more extensive forest clearing for agricultural reasons. No relationship was found between the degree of melanism and elevation, and few animals were completely melanistic. Furthermore, we found that body-ratio data collection through photographs is biased and requires physical measuring instead. Although the population size appears larger than previously surmised, the limited nesting sites and extremely low presence of juvenile and hatchling iguanas (2.4%), is similarly worrying as the situation for I. delicatissima on neighboring St. Eustatius. The islands feral cat and large goat population are suspected to impact nest site quality, nest success, and hatchling survival. These aspects require urgent future research to guide necessary conservation management.

ecology↗