Coraciidae (1 Viewer)

[Jim LeNomenclatoriste]

Ulf S. Johansson, Martin Irestedt, Per G.P. Ericson (2023). Patterns of phylogenetic diversification in the Dollarbird (Eurystomus orientalis) and Azure Roller (Eurystomus azureus) complex.Molecular Phylogenetics and Evolution. Available online 22 August 2023, 107909. In Press, Journal Pre-proof.


Patterns of phylogenetic diversification in the Dollarbird (Eurystomus orientalis) and Azure Roller (Eurystomus azureus) complex



Abstract

Genetic isolation and morphological differentiation are two important factors in the speciation process that not always act in concert. A rapid morphological change in a lineage can hide its close relationship to another lineage, while slight morphological differentiation between two taxa can give the appearance of a closer relationship than is actually the case. The Dollarbird (Eurystomus orientalis) and the Azure Roller (Eurystomus azureus) is such an example. Today the Dollarbird and the Azure Roller are unanimously considered to constitute two distinct species, but in a recent genetic study it has been shown that the latter taxon, despite being larger and having a distinctly different coloration, is phylogenetically nested within the former. Its precise placement within this complex has not been determined, however.

In this study, we investigate the phylogenetic relationships within the Dollarbird/Azure Roller complex. We estimate divergence times and infer phylogenetic relationships using sequence data from 6,475 genome-wide intronic regions, as well as complete mitochondrial genomes, using both concatenation and multispecies coalescence approaches.

We find that within the Dollarbird/Azure Roller complex there are several examples of discrepancies between genetic and morphological differentiation. The Dollarbird is currently divided into between nine to twelve subspecies. Some of these subspecies are poorly differentiated, whereas others are morphologically more clearly discernable. Our data suggest that the complex consist of at least seven distinct genetic lineages that do not entirely match the morphological variation within the group.

For instance, our results show that the subspecies solomonensis from the Solomon Islands, despite being morphologically very similar to its geographically closest neighbors, in fact is a highly distinct lineage that became isolated more than 700,000 years ago. In contrast, the morphologically distinct Azure Roller, which is currently treated as a distinct species, is nested within the Dollarbird and forms a slightly younger lineage than solomonensis and is the sister group to a clade with Australian and New Guinean Dollarbirds. Our results also show a deep genetic split within the Dollarbirds on the Asian mainland. This stands in contrast to the apparent clinal morphological variation reported for the birds on the Asian mainland.

We also find support for the presence of a genetically distinct clade in the Wallacea region. The birds from the Wallacea region has previously been recognized as a distinct subspecies, connectens, but is currently placed in synonymy of other subspecies.

Our results are thus at odds with the current division of the Dollarbird/Azure Roller complex into two species. Given that the species status of azureus is undisputed, the apparent genetic isolation of solomonensis and its clear separation from the other lineages suggests that this taxon also warrants species status. Based on the genetic and morphological variation observed within the Dollarbird/Azure Roller complex there is little doubt that even more taxa should regarded as species, but this require further examination.

 

[Jim LeNomenclatoriste]

Ulf S. Johansson, Martin Irestedt, Per G.P. Ericson (2023). Patterns of phylogenetic diversification in the Dollarbird (Eurystomus orientalis) and Azure Roller (Eurystomus azureus) complex.Molecular Phylogenetics and Evolution. Available online 22 August 2023, 107909. In Press, Journal Pre-proof.


Patterns of phylogenetic diversification in the Dollarbird (Eurystomus orientalis) and Azure Roller (Eurystomus azureus) complex



Abstract

Genetic isolation and morphological differentiation are two important factors in the speciation process that not always act in concert. A rapid morphological change in a lineage can hide its close relationship to another lineage, while slight morphological differentiation between two taxa can give the appearance of a closer relationship than is actually the case. The Dollarbird (Eurystomus orientalis) and the Azure Roller (Eurystomus azureus) is such an example. Today the Dollarbird and the Azure Roller are unanimously considered to constitute two distinct species, but in a recent genetic study it has been shown that the latter taxon, despite being larger and having a distinctly different coloration, is phylogenetically nested within the former. Its precise placement within this complex has not been determined, however.

In this study, we investigate the phylogenetic relationships within the Dollarbird/Azure Roller complex. We estimate divergence times and infer phylogenetic relationships using sequence data from 6,475 genome-wide intronic regions, as well as complete mitochondrial genomes, using both concatenation and multispecies coalescence approaches.

We find that within the Dollarbird/Azure Roller complex there are several examples of discrepancies between genetic and morphological differentiation. The Dollarbird is currently divided into between nine to twelve subspecies. Some of these subspecies are poorly differentiated, whereas others are morphologically more clearly discernable. Our data suggest that the complex consist of at least seven distinct genetic lineages that do not entirely match the morphological variation within the group.

For instance, our results show that the subspecies solomonensis from the Solomon Islands, despite being morphologically very similar to its geographically closest neighbors, in fact is a highly distinct lineage that became isolated more than 700,000 years ago. In contrast, the morphologically distinct Azure Roller, which is currently treated as a distinct species, is nested within the Dollarbird and forms a slightly younger lineage than solomonensis and is the sister group to a clade with Australian and New Guinean Dollarbirds. Our results also show a deep genetic split within the Dollarbirds on the Asian mainland. This stands in contrast to the apparent clinal morphological variation reported for the birds on the Asian mainland.

We also find support for the presence of a genetically distinct clade in the Wallacea region. The birds from the Wallacea region has previously been recognized as a distinct subspecies, connectens, but is currently placed in synonymy of other subspecies.

Our results are thus at odds with the current division of the Dollarbird/Azure Roller complex into two species. Given that the species status of azureus is undisputed, the apparent genetic isolation of solomonensis and its clear separation from the other lineages suggests that this taxon also warrants species status. Based on the genetic and morphological variation observed within the Dollarbird/Azure Roller complex there is little doubt that even more taxa should regarded as species, but this require further examination.

Either azureus is a subspecies of orientalis or many subspecies are raised to species rank

 

[Xenospiza]

Either azureus is a subspecies of orientalis or many subspecies are raised to species rank

I think it is time to ditch the old "species must be monophyletic" nonsense.

 

[Jim LeNomenclatoriste]

I think it is time to ditch the old "species must be monophyletic" nonsense.

Les espèces doivent être monophylétiques 😏😏 I wait a response from Ulf Johansson

 

[Xenospiza]

Les espèces doivent être monophylétiques 😏😏 I wait a response from Ulf Johansson

Non.

 

[Jim LeNomenclatoriste]

Non.

Otherwise, there are not species anymore. Genera, monophyletic or not ?

 

[Fred Ruhe]

Do you have to pay for every word?

Fred

 

[Mysticete]

I think it is time to ditch the old "species must be monophyletic" nonsense.

I don't think a lot of folks adhered to that "nonsense" to begin with when it comes to species. Genera, families, etc yes, species no. It's a blatant expectation from evolutionary theory that a most new species will evolve from a specific population of organisms with a much broader distribution. This is especially true with island birds, whose closest relatives are usually the birds geographically closest to them.

A good example of this principle in action is the polar bear, which apparently evolved from a specific population of brown bears in the Bering Sea region. A strict application of the phylogenetic species concept would require splitting the brown bear into numerous species, many of which would be poorly separable from other brown bears.

Monophyly has a of course: If different populations are scattered across a tree and are sister to other taxa considered good species, that would be a good case where using a phylogeny to argue for species status is appropriate.

 

[Jim LeNomenclatoriste]

. It's a blatant expectation from evolutionary theory that a most new species will evolve from a specific population of organisms with a much broader distribution. This is especially true with island birds, whose closest relatives are usually the birds geographically closest to them.

Can a species born from a population belonging to a subspecies of a related species? (My question is clear ? 😅)

 

[Mysticete]

Can a species born from a population belonging to a subspecies of a related species? (My question is clear ? 😅)

?

 

[Jim LeNomenclatoriste]

?

I knew my question was complicated or poorly written 😂

 

[Mysticete]

I knew my question was complicated or poorly written 😂

I think you are asking, can a species be more related to a subspecies of another species? If so yes.

IIRC, one of the Andean grebe species (name is escaping me which one, and I have to head out) is more closely related to the North American subspecies of Eared Grebe than it is the old world subspecies of Eared Grebe. Which is to be expected since isolated mountain lakes are basically "islands" for grebes, so we would expect the source population to be an existing nearby population.

This was justification that TiF used for split the Old vs New World subspecies of Eared Grebe, but differences between Old and New World are pretty slight and its hard argue for their recognition under any concept but PSC.

Note that this doesn't really necessarily rule out that additional splits of island populations of Dollarbird, to return to the original topic!

 

[THE_FERN]

I don't understand the question either. But:

Species arise from other species, occasionally through hybridisation between 2 species. Hybrid species include Italian sparrow (sometimes contribution of one parent vastly outweighs the other ). Digging beneath the surface, we may find that different genes within a species have different "closest relatives" and patterns of relatedness: it's one reason we are wary of single gene phylogenies. The overall phylogeny is some "average" of these histories.

Usually we cannot say whether the original "parent" form persists with any certainty since all lineages are evolving all the time. We can often say roughly when the split between lineages occurred though.

Afaik, hybridisation is the only way genes of another species can enter into a species which has split from an ancestral stock.

(In the Grebe example [which presumably refers to the extinct Colombian Grebe], I see no need to split the species. The research is just showing that the Colombian sub/species has a disjunct range---which we knew already. If we anyway do want to split the new world forms off from old, it just demonstrates this taxon goes with the latter)