• Welcome to BirdForum, the internet's largest birding community with thousands of members from all over the world. The forums are dedicated to wild birds, birding, binoculars and equipment and all that goes with it.

    Please register for an account to take part in the discussions in the forum, post your pictures in the gallery and more.
ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Saltmarsh and Nelson's Sparrows (1 Viewer)

Dan

How is a deposited vocal recording 123 of Scytalopus sp, specimen no, XYZ going to be repeatable? Am I supposed to take on trust that specimen No XYZ did indeed make the vocals attributed to it in recording 123. How is that repeatable at the level of the individual?

If you then argue this could be replicated by sampling the population, then that is surely the same as a repeat of the Sparrow study, using different individuals?

cheers, alan

You make a good point Alan. There is a degree of faith we all need to place in the accuracy of what is said in scientific publications. But in your Scytalopus example, one can review the evidence and test the conclusions the authors present. In the sparrow example, one would have to start from scratch and see if one could reconstruct the entire study. There is a difference. So my question to you is: which study would you put more faith in and adjust your checklist by? Or are they the same in your eyes?
 
You make a good point Alan. There is a degree of faith we all need to place in the accuracy of what is said in scientific publications. But in your Scytalopus example, one can review the evidence and test the conclusions the authors present. In the sparrow example, one would have to start from scratch and see if one could reconstruct the entire study. There is a difference. So my question to you is: which study would you put more faith in and adjust your checklist by? Or are they the same in your eyes?

They are clearly not the same. The hypothetical Scytalopus study was obviously just to tease out a point. I've seen and recorded enough Scytalopus over the last 25 years to accept (trust) the conclusions of the leading authors in this specialist area.

I do agree that the veracity of the Sparrow study would be greatly increased with photo-documentation to back up the scoring, although a greater failing in the Sparrow study (in my opinion) was not to study across the entire breeding range of the species group.

cheers, alan
 
Hybridisation

Walsh, Shriver, Olsen, O'Brien & Kovach 2015. Relationship of phenotypic variation and genetic admixture in the Saltmarsh–Nelson's sparrow hybrid zone. Auk 132(3): 704–716. [abstract] [pdf]
Walsh, Rowe, Olsen, Shriver & Kovach (in press). Genotype-environment associations support a mosaic hybrid zone between two tidal marsh birds. Ecol Evol. [abstract] [pdf]
 
Hybridisation

Walsh, Shriver, Olsen & Kovach 2016. Differential introgression and the maintenance of species boundaries in an advanced generation avian hybrid zone. BMC Evol Biol 16: 65. [article & pdf]

Gives a 'hybrid index' for the most significant New England coastal marshes (ME–CT).
 
Last edited:
Jennifer Walsh, Brian J. Olsen, Katharine J. Ruskin, W. Gregory Shriver, Kathleen M. O'Brien and Adrienne I. Kovac. Extrinsic and intrinsic factors influence fitness in an avian hybrid zone. The Linnean Society of London, Biological Journal of the Linnean Society, 2016, 00, 000–000.

[abstract]
 
Walsh, Lovette, Winder, Elphick, Olsen, Shriver, Kovach. [In press.] Subspecies delineation amid phenotypic, geographic, and genetic discordance in a songbird. Mol. Ecol.
[abstract]
 
Last edited:
Walsh, Shriver, Correll, Olsen, Elphick, Hodgman, Rowe, O’Brien, Kovach. 2017. Temporal shifts in the saltmarsh–Nelson’s sparrow hybrid zone revealed by replicated demographic and genetic surveys. Conserv Genet 18:453-466.
[abstract & supp info]
 
Jennifer Walsh, Logan M. Maxwell, and Adrienne I. Kovach (2018) The role of divergent mating strategies, reproductive success, and compatibility in maintaining the Saltmarsh–Nelson's sparrow hybrid zone. The Auk: July 2018, Vol. 135, No. 3, pp. 693-705.

Abstract:

Understanding inter- and intra-specific variation in mate compatibility and reproductive success can offer insight into the factors driving sexual selection, behavioral dynamics, and isolating mechanisms across natural populations. This information is particularly relevant when trying to understand the patterns that shape the causes and outcomes of hybridization in natural systems. We evaluated mating patterns and male reproductive success in a hybrid zone between the Saltmarsh (Ammodramus caudacutus) and Nelson's sparrow (A. nelsoni). Specifically, we investigated variation in male reproductive success between pure Saltmarsh and pure Nelson's sparrows and between pure and hybrid males, while testing for assortative vs. random mating. DNA samples were collected from adults (n = 342) and nestlings (n = 348), and paternity analyses and assignment of individuals to pure and hybrid classes were conducted using 11 microsatellite loci. We documented high promiscuity and reproductive skew in Saltmarsh and Nelson's sparrow males, with greater skew in Saltmarsh Sparrows. Across Nelson's Sparrow and hybrid individuals, we documented a significant correlation between reproductive success and genetic heterozygosity. F1–F2 hybrid males exhibited significantly lower reproductive success (number of offspring sired) compared with pure individuals, and Saltmarsh and Nelson's sparrows exhibited strong patterns of assortative mating. We conclude that differences in reproductive success among pure and hybrid individuals, coupled with strong assortative mating, are shaping hybrid zone dynamics in this system and may be important for maintaining species boundaries.
 
Walsh J, Kovach AI, Olsen BJ, Shriver WG, Lovette IJ. 2018. Bidirectional adaptive introgression between two ecologically divergent sparrow species. Evolution.
[abstract & supp.info.]

Abstract
Natural hybrid zones can be used to dissect the mechanisms driving key evolutionary processes by allowing us to identify genomic regions important for establishing reproductive isolation and that allow for transfer of adaptive variation. We leverage whole‐genome data in a system where two bird species, the saltmarsh (Ammospiza caudacuta) and Nelson's (A. nelsoni) sparrow, hybridize despite their relatively high background genetic differentiation and past ecological divergence. Adaptive introgression is plausible in this system because Nelson's sparrows are recent colonists of saltwater marshes, compared to the specialized saltmarsh sparrow that has a longer history of saltmarsh adaptation. Comparisons among whole‐genome sequences of 34 individuals from allopatric and sympatric populations show that ongoing gene flow is shaping the genomic landscape, with allopatric populations exhibiting genome‐wide FST estimates close to double of that observed in sympatry. We characterized patterns of introgression across the genome and identify regions that exhibit biased introgression into hybrids from one parental species. These regions offer compelling candidates for genes related to tidal marsh adaptations suggesting that adaptive introgression may be an important consequence of hybridization. These findings highlight the value of considering the landscapes of both genome‐wide introgression and divergence when characterizing the evolutionary forces that drive speciation.
 
Warning! This thread is more than 6 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.

Users who are viewing this thread

Back
Top