Showing posts with label birds. Show all posts
Showing posts with label birds. Show all posts

Friday, April 5, 2013

Updated information about lab-meeting on April 9: ERC, phylogenies and tropical diversification

This is an update about the coming lab-meeting on Tuesday April (10.30), as there was some mis-communication, and it turns out Lesley will not be able to attend the meeting due to a course in landscape genetics, and this is probably also the case for Rachel and Maren. The lab-meeting on Tuesday will start with  Jessica presenting her ERC-talk for the coming interview in Brussels, and she can then get final feedback from the lab-members that attend. Our new student Anais from Cataluna has also promised to bring some catalunian "fika", and we can try out the red wine she brought last week.

Then, we should discuss this paper that I originally suggested which deals with how the use of multiple phylogenies can be used to answer basic ecological and evolutionary questions about the niche conservatism and range expansions and test the classical "tropical conservatism" hypothesis. This paper is in press in Evolution, and is quite long, but in case you have time you can also read the shorter paper Lesley suggested that was published in Ecology Letters. 

Both these papers are thematically similar and demonstrate the power of a phylogenetic perspective and modern comparative methods to address fundamental problems and general processes in ecology and evolution. The titles and abstracts of both papers are posted below. Enjoy!

WHAT CAN MULTIPLE PHYLOGENIES SAY ABOUT THE LATITUDINAL DIVERSITY GRADIENT? A NEW LOOK AT THE TROPICAL CONSERVATISM, OUT OF THE TROPICS, AND DIVERSIFICATION RATE HYPOTHESES



We reviewed published phylogenies and selected 111 phylogenetic studies representing mammals, birds, insects, and flowering plants. We then mapped the latitudinal range of all taxa to test the relative importance of the tropical conservatism, out of the tropics, and diversification rate hypotheses in generating latitudinal diversity gradients. Most clades originated in the tropics, with diversity peaking in the zone of origin. Transitions of lineages between latitudinal zones occurred at 16–22% of the tree nodes. The most common type of transition was range expansions of tropical lineages to encompass also temperate latitudes. Thus, adaptation to new climatic conditions may not represent a major obstacle for many clades. These results contradict predictions of the tropical conservatism hypothesis (i.e., few clades colonizing extratropical latitudes), but support the out-of-the-tropics model (i.e., tropical originations and subsequent latitudinal range expansions). Our results suggest no difference in diversification between tropical and temperate sister lineages; thus, diversity of tropical clades was not explained by higher diversification rates in this zone. Moreover, lineages with latitudinal stasis diversified more compared to sister lineages entering a new latitudinal zone. This preserved preexisting diversity differences between latitudinal zones and can be considered a new mechanism for why diversity tends to peak in the zone of origin.




  • Alex L. Pigot*, 
  • Joseph A. Tobias



  • Whether biotic interactions limit geographic ranges has long been controversial, and traditional analyses of static distribution patterns have made little progress towards resolving this debate. Here, we use a novel phylogenetic approach to test whether biotic interactions constrain the transition to secondary sympatry following speciation. Applying this temporal framework to a diverse clade of passerine birds (Furnariidae), we reject models of geographic range overlap limited purely by dispersal or environmental constraints, and instead show that rates of secondary sympatry are positively associated with both the phylogenetic and morphological distance between species. Thus, transition rates to sympatry increase with time since divergence and accelerate as the ecological differences between species accumulate. Taken together, these results provide strong empirical evidence that biotic interactions – and primarily ecological competition – limit species distributions across large spatial and temporal scales. They also offer phylogenetic and trait-based metrics by which these interactions can be incorporated into ecological forecasting models.

    Sunday, March 18, 2012

    On density-dependent diversification and speciation in birds

    Posted by Erik Svensson


    This coming Wednesday (March 21 at 13.30 NOTE TIME!!!!), we will discuss a paper about the (possible) density-dependent slowdown of cladogenesis in birds with the progress of adaptive radiation. It is a paper that was published relatively recently, although it is not entirely new, in PLoS Biology by Albert Phillimore and Trevor D. Price. The title of the paper is:
    "Density-Dependent Cladogenesis in Birds"
    The authors have used molecular phylogenies from various avian groups to test the hypothesis that diversification rates decline with the progress of adaptive radiation, and as we are approaching the present. Here is the Abstract to the article, which can be downloaded here (PLoS Biology is a "Open Acess"-publisher, which makes everything easier):



    Abstract 




    A characteristic signature of adaptive radiation is a slowing of the rate of speciation toward the present. On the basis of molecular phylogenies, studies of single clades have frequently found evidence for a slowdown in diversification rate and have interpreted this as evidence for density dependent speciation. However, we demonstrated via simulation that large clades are expected to show stronger slowdowns than small clades, even if the probability of speciation and extinction remains constant through time. This is a consequence of exponential growth: clades, which, by chance, diversify at above the average rate early in their history, will tend to be large. They will also tend to regress back to the average diversification rate later on, and therefore show a slowdown. We conducted a meta-analysis of the distribution of speciation events through time, focusing on sequence-based phylogenies for 45 clades of birds. Thirteen of the 23 clades (57%) that include more than 20 species show significant slowdowns. The high frequency of slowdowns observed in large clades is even more extreme than expected under a purely stochastic constant-rate model, but is consistent with the adaptive radiation model. Taken together, our data strongly support a model of density-dependent speciation in birds, whereby speciation slows as ecological opportunities and geographical space place limits on clade growth.

    We meet at 13.30 (not 13.00!) to discuss this interesting article.

    Sunday, February 20, 2011

    On intra- and interlocus sexual conflict in birds and plants

    This week's lab-meeting (Wednesday February 23, 13.30-15.00), will be dedicated to sexual conflict, both intralocus and interlocus sexual conflict. PhD-students Maja Tarka and Josefin Madjidian want to have some input on their manuscripts, which deals with these topics in warblers and plants, respectively. Please contact Maja (maja.tarka@zooekol.lu.se) and Josefin (Josefin.Madjidian@ekol.lu.se) to get copies of their manuscripts, well before Wednesday, so that you have time to read and give input.

    Any fika volunteer?