Phylogeny and evolutionary history of the amniote egg

Starck, J. Matthias; Stewart, James R.; Blackburn, Daniel G.

doi:10.1002/jmor.21380

“…Macroevolutionary patterns in amniote reproduction ( Battistella et al, 2019 ; Murray, Crother & Doody, 2020 ; Starck, Stewart & Blackburn, 2021 ) can be investigated based on the diversity of traits in egg and clutch ( e.g ., Kaplan & Salthe, 1979 ; Deeming & Birchard, 2007 ; Jetz, Sekercioglu & Böhning-Gaese, 2008 ; Deeming & Ruta, 2014 ). The idea of an “optimal” correlation between egg and clutch size, based on trade-offs associated to K/r strategies, has led to several discussions without a consensus about the distribution or reasons of such correlations ( Smith & Fretwell, 1974 ; Congdon & Gibbons, 1987 ; Wilbur & Morin, 1988 ; Elgar & Heaphy, 1989 ; Godfray, Partridge & Harvey, 1991 ; Kuchling, 1999 ; Zhao, Chen & Liao, 2017 ; Yu & Deng, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

The evolution of reproductive strategies in turtles

Jorgewich-Cohen

¹

,

Henrique

²

,

Dias

³

et al. 2022

PeerJ

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Optimal egg size theory assumes that changes in the egg and clutch are driven by selection, resulting in adjustments for the largest possible production of offspring with the highest fitness. Evidence supports the idea that large-bodied turtles tend to produce larger clutches with small and round eggs, while smaller species produce small clutches with large and elongated eggs. Our goals were to investigate whether egg and clutch size follow the predictions of egg size theory, if there are convergent reproductive strategies, and identify ecological factors that influence clutch and egg traits across all clades of living turtles. Using phylogenetic methods, we tested the covariance among reproductive traits, if they are convergent among different turtle lineages, and which ecological factors influence these traits. We found that both egg shape and size inversely correlate with clutch size, although with different evolutionary rates, following the predictions of the egg size theory. We also present compelling evidence for convergence among different turtle clades, over at least two reproductive strategies. Furthermore, climatic zone is the only ecological predictor to influence both egg size and fecundity, while diet only influences egg size. We conclude that egg and clutch traits in Testudines evolved independently several times across non-directly related clades that converged to similar reproductive strategies. Egg and clutch characteristics follow the trade-offs predicted by egg size theory and are influenced by ecological factors. Climatic zone and diet play an important role in the distribution of reproductive characteristics among turtles.

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“…In this study, we sampled within 8 h after oviposition, when microbiota have just colonized the surface of the egg. We do not know which bacteria can continue to survive and thrive on eggshells or whether these thriving bacteria cross the eggshell barrier, as its permeability increases with the absorption of calcium during embryonic development to help embryos shape their symbiotic microbiota ( Sexton et al, 2005 ; Solomon, 2010 ; Starck et al, 2021 ). Illustrating the assembly dynamics of microbiota on eggshells during embryo development until hatching will be essential to better understand their function in transgenerational transmission of symbiotic microbiota.…”

Section: Discussionmentioning

confidence: 99%

Mixed-Mode Bacterial Transmission via Eggshells in an Oviparous Reptile Without Parental Care

Li

¹

,

Yang

²

,

Li

³

et al. 2022

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Symbiotic microorganisms play important roles in maintaining health and facilitating the adaptation of the host. We know little about the origin and transgenerational transmission of symbiotic bacteria, especially in egg-laying species without parental care. Here, we investigated the transmission of bacterial symbionts in the Chinese three-keeled pond turtle (Mauremys reevesii), a species with no post-oviposition parental care, by evaluating contributions from potential maternal and environmental sources to eggshell bacterial communities. Using 16S rRNA amplicon sequencing, we established that the bacterial communities of eggshells were similar to those of the maternal cloaca, maternal skin, and nest soil, but distinct from those of surface soil around nest and pond water. Phylogenetic structure analysis and source-tracking models revealed the deterministic assembly process of eggshell microbiota and high contributions of the maternal cloaca, maternal skin, and nest soil microbiota to eggshell bacterial communities. Moreover, maternal cloaca showed divergent contribution to eggshell microbiota compared with two other main sources in phylogenesis and taxonomic composition. The results demonstrate a mixture of horizontal and vertical transmission of symbiotic bacteria across generations in an oviparous turtle without parental care and provide insight into the significance of the eggshell microbiome in embryo development.

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“…A calcified eggshell is an ancestral trait for Sauropsida (D'Alba et al, 2021; Stewart, 1997; Starck et al, 2021) and this structure predates the separation of lineages leading to either snakes or birds. Alternative hypotheses of sauropsid phylogeny either place turtles as basal (Gauthier et al, 1988; Lee, 2001) or a lineage comprised of turtles and archosaurs as sister taxon to lepidosaurs (Chiari et al, 2012; Crawford et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…A calcified eggshell is an ancestral trait for Sauropsida (D'Alba et al, 2021;Stewart, 1997;Starck et al, 2021) and this structure predates the separation of lineages leading to either snakes or birds.…”

Section: Evolutionary Implicationsmentioning

confidence: 99%