High Connectivity Among Breeding Populations of the Elegant Tern (Thalasseus elegans) in Mexico and Southern California Revealed Through Population Genomic Analysis

Perez, Gabriella S.; Goodenough, Katharine S.; Horn, Michael H.; Patton, Robert T.; Ruíz, Enrico A.; Velarde, Enriqueta; Aguilar, Andres

doi:10.1675/063.043.0102

Cited by 6 publications

(3 citation statements)

References 51 publications

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“…Diversity metrics recovered by both markers, as represented by allelic richness and observed heterozygosity, were low compared to other super-abundant seabird species (Wojczulanis-Jakubas et al 2015, Yannic et al 2016), but were largely consistent with studies of other breeding gulls and terns (Perez et al 2020) and were comparable to past assessments of roseate tern genetic diversity (Lashko 2004;Dayton & Szczys 2021). Results from SNP markers suggested that all 4 sampling locations showed evidence of recent declines, consistent with known population declines in both the early and mid-20 th century for the Northwestern population (USFWS 2020) and probable declines in the Florida and USVI populations.…”

Section: Discussionsupporting

confidence: 76%

Conservation Genomics Reveals Low Connectivity Among Populations of Threatened Roseate Terns in the Atlantic Basin

Byerly

Chesser

Fleischer

et al. 2021

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While the effects of barriers to dispersal such as population declines, habitat fragmentation, and geographic distance have been well-documented in terrestrial wildlife, factors impeding the dispersal of highly vagile taxa such as seabirds are less well understood. The roseate tern (Sterna dougallii) is a globally distributed seabird species, but populations tend to be both fragmented and small, and the species is declining across most of its range. Within the Atlantic Basin, past work has shown differentiation among roseate terns breeding on different continents, but these results were generated with a limited number of microsatellite markers. Relationships between breeding populations in the Northwestern Atlantic and the Caribbean have never been analyzed. We evaluated population structuring of roseate tern populations in North America and the Azores using both microsatellite markers and single-nucleotide polymorphisms generated through targeted sequencing of Ultra-conserved Elements. For both marker types, we found significant genetic differentiation among all 3 populations and evidence for moderate contemporary unidirectional gene flow from the Caribbean to the Azores, but not among other populations. Within the Caribbean metapopulation, we found high rates of unidirectional migration from the Virgin Islands to Florida, potentially indicative of movement from source population to sink or an artifact of dispersal among other unsampled populations in the Caribbean region. These observations have significance for species persistence in the Atlantic, as our results suggest that loss of genetic diversity within populations is unlikely to be buffered by inflow of new alleles from other breeding populations.

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Section: Discussionsupporting

confidence: 76%

Conservation Genomics Reveals Low Connectivity Among Populations of Threatened Roseate Terns in the Atlantic Basin

Byerly

Chesser

Fleischer

et al. 2021

Preprint

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“…Another important factor for the continued increase in the species population size may be their ability to shift nesting sites when conditions in one area are adverse. Through genetic analysis and banding information Perez et al (2020) have shown that individual elegant terns move freely between the Gulf of California and Southern California nesting sites, and this may be occurring in response to local conditions of food availability. Our model results (Tables 2, 3) show that population size in the core area was the primary driver of vagrancy to the east coast (H3) and Europe (H4), and El Niño was not influential, whereas both population size and El Niño were drivers for northward dispersal to the Pacific Northwest.…”

Section: Discussionmentioning

confidence: 99%

Population Growth and Long-Distance Vagrancy Leads to Colonization of Europe by Elegant Terns Thalasseus elegans

et al. 2021

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Elegant terns Thalasseus elegans breed in a very limited area of the northern Gulf of California and the Pacific coast of southern California, with up to 95% (mean 78%, 1991–2014, Perez et al., 2020) of the population nesting on Isla Rasa in the northern Gulf of California. On Isla Rasa, the primary nesting colony, elegant terns suffered predation by rodents which raised the possibility of population extinction, with a substantial proportion of the world population nesting on this single island. Because of this threat, rodents were successfully removed from Isla Rasa in 1995. The removal of rodents from Isla Rasa led to a near immediate increase in the population of elegant terns. That increase was associated with a changing pattern in dispersal by the terns, including extraordinary movements to the Gulf of Mexico, the Atlantic coast of the United States north to Massachusetts, and, remarkably, to western Europe. A few elegant terns successfully bred at these European localities during 2009 to the present. In this paper we use this exceptional example of long-distance dispersal to illustrate how rapid population growth during ∼ 1995 to present can lead to successful colonization of remote sites through repeated instances of vagrancy. We tested four Hypotheses that together support the idea that the growing population of elegant terns has produced increasing numbers of young, and these young have spread, through the mechanism of vagrancy, to the Pacific Northwest, the east coast of the United States, and western Europe. Our Hypotheses are: (1) The nesting population of elegant terns within their core nesting range has increased since removal of rodents from Isla Rasa; (2) Occurrence of vagrant elegant terns in the Pacific Northwest is driven by population growth within the core breeding range. (3) Occurrence of vagrant elegant terns at the east coast of the United States is driven by population growth within the core breeding range. (4) Occurrence and colonization of western Europe by elegant terns is driven by nesting population size within the core breeding range. Corollaries of these Hypotheses are, (i) that there is a time lag in occurrence of vagrants at each of these areas, based on increasing distance from the core breeding range and (ii) the number of vagrants in any given year is also related to sea surface temperature (SST), as expressed by Oceanic Niño Index, a proxy for food resource levels. Generally we found strong statistical support for each of these Hypotheses; an exception was for the occurrence of elegant terns in the Pacific Northwest, which initially occurred following El Niño events (low food supply) and profound breeding failure, but later corresponding to cold water years with high breeding success. We use elegant terns, exceptional for the highly restricted breeding range and sustained population growth over 25 years, to illustrate how growing populations may colonize very distant habitats through repeated instances of vagrancy.

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“…In this sense, two scenarios can be expected: (1) Weak genetic differentiation provided by the seabird's ability to fly long distances, leading to panmixia [21,22]. For example, in the Elegant Tern (Thalasseus elegans), high connectivity among populations was revealed between the Gulf of California and southern California, with no significant genetic differentiation, even though their colonies are separated by land barriers and breed in different ocean regimes [23]. (2) Genetic structure can be noticed even in small areas due to philopatry and local selection pressures [5,24].…”

Section: Introductionmentioning

confidence: 99%

Strong Philopatry, Isolation by Distance, and Local Habitat Have Promoted Genetic Structure in Heermann’s Gull

et al. 2022

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Philopatry can promote genetic differentiation among populations but remains undescribed in many seabirds. Hence, we explored such associations in Heermann’s Gull. Philopatry was observed monitoring 998 gulls in Rasa Island, while genetic differences were examined in the Cardonosa, Rasa, and Isabel islands using the cytochrome b of 296 gulls. Adults returned repeatedly to its natal valley or to a very close distance from it under different modelled hypotheses. Likewise, the interaction between sex and distance indicated significant male-biased philopatry. Besides, low to high genetic differentiation was observed between the Rasa and Cardonosa islands (ΦST = 0–0.22) (both in the Midriff Islands Region), but higher genetic differentiation against Isabel Island (ΦST > 0.25) (in the Mexican Province region). Consistently, genetic structure among regions was observed using different approaches (AMOVA: ΦCT = 0.49; SAMOVA: FCT = 0.49; and BAPS: K = 2). Similarly, a pattern of isolation by distance (rM= 0.82, p = 0.03), agrees with lower estimates of scaled migration rates between regions than among islands of the same region. Overall, it is suggested that the genetic structure found in Heermann’s Gull has been promoted by physical and behavioral barriers.

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High Connectivity Among Breeding Populations of the Elegant Tern (Thalasseus elegans) in Mexico and Southern California Revealed Through Population Genomic Analysis

Cited by 6 publications

References 51 publications

Conservation Genomics Reveals Low Connectivity Among Populations of Threatened Roseate Terns in the Atlantic Basin

Conservation Genomics Reveals Low Connectivity Among Populations of Threatened Roseate Terns in the Atlantic Basin

Population Growth and Long-Distance Vagrancy Leads to Colonization of Europe by Elegant Terns Thalasseus elegans

Strong Philopatry, Isolation by Distance, and Local Habitat Have Promoted Genetic Structure in Heermann’s Gull

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