New Guinean passerine birds (1 Viewer)

Knud Andreas Jønsson, Andrew Hart Reeve, Mozes P. K. Blom, Martin Irestedt & Petter Zahl Marki (2019) Unrecognised (species) diversity in New Guinean passerine birds, Emu - Austral Ornithology, DOI: 10.1080/01584197.2019.1581033

Abstract:

Species represent an important unit for the study of diversity, but may not always be delimited consistently across regions and clades. Many of these taxonomic inconsistencies are due to the variable views of taxonomists. In recent years, however, new methodologies have attempted to circumvent this problem by assigning more objective criteria for the delimitation of species, drawing on a wide range of data such as DNA, morphology, vocalisation and ecology. Here, we apply a genetic screening approach in which we sequence the mitochondrial gene ND2 for all recognised subspecies of 16 species in eight genera (a mix of lowland and montane species) from the geologically complex tropical island of New Guinea. We show that populations within some species are genetically highly divergent despite little morphological differentiation, but we also find an example in which populations from five morphologically distinct species are genetically very similar. Overall, our data show higher levels of genetic differentiation than expected, but also highlight the difficulty of predicting which groups contain unrecognised diversity. These results are interesting in their own right, but also have implications for further analyses that focus on increasing our understanding of how diversity builds up over time.

I expect that if somebody looks at genetic difference within rainforest birds in South America which are widespread but sedentary and drab-colored, one finds similar genetically divergent lineages. Which would parallel small mammals. Latter is to be expected, since genetic processes should be almost identical in small sedentary birds and rodents.

The question is: do we want to have 5 fold or 10 times more species of small birds? The additional problem is that we have no idea where geographic boundaries between those genetic lineages go. Mammal people dealing with diversity of rodents or shrews said no.

I would think the question less 'do we want to have' and more 'is the available data better represented by species definitions which lead to'. Surely the goal of science is not wish fulfillment, but ever improving models of observational data?

(Also, I'll note that many of the studies which are finding strong genetic divergence in South America have found these linked to barriers to dispersal such as large rivers - suggesting both that there may indeed be cryptic species present, and that the geographic boundaries separating them may not be so difficult to discern after all.)

jurek said:

The question is: do we want to have 5 fold or 10 times more species of small birds? The additional problem is that we have no idea where geographic boundaries between those genetic lineages go. Mammal people dealing with diversity of rodents or shrews said no.

Click to expand...

What actual facts are you basing this comment on? none I assume as in reality the situation is very much the opposite when it comes to small mammal taxonomy. There have been massive increases in the number of reckognized rodents/insectivores in the last decade alone largely thanks to thorough studies similar to the one detailed in this paper.

Actualy increase of number of species of rodents is smaller than birds. And it occurs by actual collecting new animals from poorly studied localities. New rodents are mostly discovered, but new birds are mostly split.

Small mammals have e.g. chromosomal races, which in birds would perhaps automatically be called new species. However in rodents there can be multiple such races in a mid-sized temperate country.

Which is an example of a glitch in science - it is easier to split an existing species than go out and discover a new one. Which is now discovery of new knowledge of biodiversity is harmed by maximizing papers published.