speciation
grrlscientist | February 22, 2008tags: Charles Darwin, crabs, crustaceans, University of Oxford, Oxford Museum of Natural History, online database
Fiddler crabs are easily recognised by their distinctive asymmetric claws. This specimen was captured in May 1835 when the Beagle arrived in Mauritius.
Image: Oxford University Museum of Natural History [larger view].
The University of Oxford Museum of Natural History has electronically catalogued Charles Darwin's crabs that had been collected by the famous naturalist while he was making his voyage around the world on the HMS Beagle from 1831 to 1836.
These crustaceans were…
grrlscientist | February 5, 2008tags: researchblogging.org, birds, Nepal Rufous-vented Prinia, Prinia burnesii nipalensis, ornithology, speciation, new species, Nepal
A new subspecies of the Rufous-vented Prinia, Prinia burnesii,
has been found in Nepal. This new bird is now known as the
Nepal Rufous-vented Prinia, Prinia burnesii nipalensis.
[larger view].
A new subspecies of bird has been discovered on marshy grasslands located on small islands in Nepal's Koshi River. This new subspecies is similar to two other previously described subspecies of the Rufous-vented Prinia that are found along rivers in Pakistan and India…
grrlscientist | January 23, 2008tags: Speciation in Birds, Trevor Price, book review, evolution, birds
The question of what is a species and how they arise has generated numerous discussions and tremendous controversy throughout the decades. This interest is more than academic, as any bird watcher will tell you since the American Ornithologists' Union (AOU) routinely splits one species into two or lumps two species into one, thereby wreaking havoc with many birders' "life lists"; that master list of species seen that is kept by each birder. More than once, I have heard birders question the validity of one or another of the…
grrlscientist | December 22, 2007tags: researchblogging.org, giraffe species, Giraffa camelopardalis, speciation, evolution, conservation, molecular phylogeny
West African giraffe, currently Giraffa camelopardalis peralta.
Image: Wikipedia (Creative Commons) [larger view]
How many species of giraffes are there? Well, it may surprise you to learn this, but some people have actually thought about this throughout the decades, and they decided that there is only one species, Giraffa camelopardalis. However, a paper published today in BMC Biology convincingly demonstrates that giraffes are actually comprised of at least six…
evolgen | July 8, 2007I've got far too many tabs open in my browser window, and I gotta blog them ASAP so that I can clean up the ol' computer. Here are a few things I've been meaning to blog, in list form:
Nature Genetics has published an issue devoted to structural variation in genomes. There appears to be a bias toward human genomes, but it's cool nonetheless. Also, I'm pretty sure all the articles are FREE ACCESS.
The most recent issue of Molecular Ecology has a bunch of articles on the genetics of speciation. There's also an article on the genetics of pigmentation variation in Drosophila melanogaster.
Peter…
evolgen | May 25, 2007For some reason, I have been collecting links to articles involving hybridization. That, on its own, would call for a massive link dump, but a recent news item makes for a nice contrast. First, the hybrids:
Where better to start than this review of hybrid speciation -- a topic I've discussed previously. The take home message: we first thought that hybrid speciation only happened in combination with polyploidy in plants, then we found out that hybrid speciation can also occur without polyploidization in plants, and then we discovered that the same thing happens in animals.
Here's an article on…
evolgen | April 27, 2007The most recent issue of the Journal of Heredity contains a bunch of articles from a symposium on the "Genetics of Speciation" organized by Loren Rieseberg. Included in the collection is an article by Allen Orr and two of his students on speciation in Drosophila, which discusses mapping speciation genes, the role of meiotic drive in speciation, and Dobzhansky Muller incompatibilities via gene translocation (the latter two are the topics of recent papers from Orr's group -- here and here). Also in the special issue is an article from Mohamed Noor's lab on mapping inversion breakpoints between…
evolgen | April 27, 2007This week's phylogeny comes from this paper on molecular dating of speciation events. I won't be addressing molecular dating per se, but I will be dealing with what molecular clocks tell us. Like, do they actually reveal the speciation time of a pair of species?
The divergence date of a pair of species can refer to two things: when the two populations became two species (no longer exchanging alleles) or when the two genetic lineages split. The splitting of genetic lineages happens prior to the speciation event. That's because within a population there is variation throughout the genome. It's…
evolgen | April 5, 2007
A recent flurry of papers (reviewed here) have presented evidence for homoploid hybrid speciation in insects -- one in Rhagoletis (a fruit fly) and two in butterflies (one in Heliconius and one in Lycaeides). The Rhagoletis paper showed that a hybrid species formed from two other species -- one that feeds on snowberries and one that feeds on blueberries -- native to North America. The hybrid species feeds on an invasive honeysuckle that was introduced from Asia within the last couple of centuries.
The paper on Heliconius butterflies described a hybrid between H. melpomene and H. cydno which…
evolgen | February 5, 2007I've been chatting up Wilkins about the role of natural selection in speciation (and when I say "speciation" I mean "reproductive isolation"). Wilkins listed a few cases where speciation would occur independently of natural selection. Amongst the mechanisms in Wilkins's list was speciation via karyotypic changes (polyploidy, inversions, fusions or fissions). I cried shenanigans, and this is why.
The karyotype refers to the organization of an organism's genome -- chromosome number, fusions/fissions of chromosomes, and gene order within chromosomes. One way to change the karyotype is to…
evolgen | January 30, 2007I straddle the line between being a population biologist and a molecular geneticist. That's a self-congratulatory way of saying that I am an expert in neither field. But existing in the state I do allows me to observe commonalities shared by both. For example, both fields have terminology (or what the uninitiated would call jargon) that lack sufficient definitions.
Amongst my minimal postings from last week were included a couple of riffs on species and speciation (the first, the second) getting at the lack of a coherent definition of species. My conclusion is that there is not, nor will…
evolgen | January 24, 2007Wilkins has replied to my post on species concepts.
The gist: there are a bunch of species concepts, many of which are pretty darn good.
My reply: that's awesome as long as they guide future research. The BSC provides a framework for studying reproductive isolation. Ecological species concepts are useful when studying adaptation to niches. But I still see nothing interesting that can be garnered from purely phylogenetic- or divergence-based species concepts.
evolgen | January 23, 2007Because I haven't riled up Wilkins in a while.
I was chatting with a friend who has published a fairly high profile article on speciation about species concepts. We came to the conclusion that species concepts are useless unless they guide future research. Okay, we were just echoing Coyne 'n Orr.
As crappy as the biological species concept is, the BSC is really good for guiding research on the evolution of pre-zygotic, intrinsic reproductive isolation. I realize this is entirely circular (the BSC states that speciation has occurred when reproductive isolation is achieved). All of the research…
evolgen | December 4, 2006We usually think of speciation as a bifurcating process -- a single lineage splitting into two. The relationships of those species can often be determined using DNA sequences. But we know that there are exceptions, like horizontal gene transfer in bacteria. And hybrid speciation in plants. These exceptions often interfere with our ability to reconstruct the evolutionary relationships of those species.
Hybrid speciation occurs when two species produce hybrids that are both fit and capable of becoming reproductively isolated from the two parental species. The new species will often exploit a…
grrlscientist | December 1, 2006
The Tree of Life
Click image for larger view.
This tree is constructed from an analysis of small subunit rRNA sequences sampled from approximately 3,000 species from throughout the Tree of Life. The species were chosen based on their availability, but most of the major taxonomic groups were included, sampled very roughly in proportion to the number of known species in each group (although many groups remain over- or under-represented).
The number of species represented is approximately the square-root of the number of species thought to exist on Earth (i.e., three thousand out of an…
evolgen | November 1, 2006Nature Reviews Genetics has published a review (go figure) of speciation genetics penned by Mohamed Noor and Jeff Feder. Here is the purpose of the review, from the horses' mouths:
Here, we review how recent advances in molecular and genomic techniques are helping to achieve a greater understanding of the genetics of speciation. For the purpose of this review, we focus on technical advances rather than theoretical concepts, which are discussed extensively elsewhere. We define speciation for sexually reproducing organisms as the transformation of within-population variation into taxonomic…
grrlscientist | October 19, 2006A friend emailed this link and even though I have only begun to poke around on it, but already I find it fascinating. Darwin OnLine is a searchable webbed database that contains more than 50,000 text pages and 40,000 images of publications and handwritten manuscripts. It also has the most comprehensive Darwin bibliography ever published and the largest manuscript catalogue ever assembled. More than 150 ancillary texts are also included, ranging from secondary reference works to contemporary reviews, obituaries, published descriptions of Darwin's Beagle specimens and important related works…
evolgen | September 22, 2006The Scientist (we're not sure which one) reviews the palm tree sympatric speciation paper from February (doi here). Here's what Jerry Coyne has to say:
"Both these cases are most parsimoniously interpreted as sympatric speciation," said Jerry Coyne at the University of Chicago. Still, he questioned whether the species are truly sister taxa, and didn't reach the island or crater lake from separate invasions from a source population. "If there's a little bit of hybridization between the species, they're going to become genetically more similar to each other than either is to a mainland species…
evolgen | August 15, 2006Here are three interesting items that I don't plan on blogging, but are worth linking to:
Here is a news release on indel variation in humans. SNPs are so 20th century. Deletions, duplications, and insertions are the molecular polymorphisms of the future.
Speaking of deletions and duplications, Nobel Intent has a good review of three articles (available here, here, and here) that deal with structural polymorphism and disease on human chromosome 17. Interestingly, the same region examined the three papers harbors an inversion that may confer a fitness benefit.
Finally, totally unrelated…
evolgen | July 16, 2006Here is some light reading for your Sunday:
Mosquitoes sing to each other by flapping their wings. This paper reports sexually dimorphic responses to wing beat patterns in mosquitoes (PZ Myers has a good review). This leads me to wonder whether we can study intra- and inter-specific differences in flight behavior and response, which then gets me wondering whether we can find QTLs responsible for these differences. And (this should come as no surprise to those who know me) I also wonder whether these QTLs will map to within inversions for sympatric species pairs more so that allopatric…