Seed dispersal by megafauna (extinct and extant)

I’ll be posting a series on megafauna (extinct and extant) and megafauna-dependent plants that I’ve been contributing to our Facebook page Frugivores & Seed Dispersal during the month of December. The posts focused on megafauna frugivores and megafauna-dependent fruits and seeds, and the processes of dispersal associated with them. I also included other interesting posts on frugivory and seed dispersal, as ever, but megafauna was the focus. Hopefully we contribute to a better appreciation of the distinct ecological roles and the contribution of megafauna species to the functioning and maintenance of ecosystems around the world, specifically on their role as frugivores and seed dispersers.

fig-9-cada-um

Among the most spectacular frugivores and seed dispersers we find the Megafauna species, those amazing beasts that impress every naturalist because of their adaptations, life histories, and specific traits. Yet megafauna species are being particularly hard hit by human-driven activities, notably hunting and deforestation. Megafauna species are traditionally defined as being above 40 kg body mass (i.e., > 100 lb), and include a full range of mammals (e.g., rhino, elephants, a number of antelopes, large primates), birds (e.g., ostrich, cassowary, emu), and reptiles (e.g., varanids, turtles). Moreover, think about the late Pleistocene (~12 Kyr BP) extinction of an even richest diversity of megafauna species: toxodons, terrestrial sloths, mamuths, gliptodons, gomphoteres, etc. The study of frugivory and seed dispersal (FSD) by megafauna opens a number of extremely interesting questions, ranging from the role of past history in shaping fruit traits, the lasting signatures of past extinctions of major seed dispersers for plants (e.g., in the genetic pools), the conflicts and interactions with humans in natural and seminatural habitats, the role of extremely long-distance seed dispersal by megafauna and its collapse following extinction, etc.

Illustration: Dadi, “Cada um”.

 

Rey Jaime I Award, Environmental Sciences


 

I’m very honored with being awarded the Rey Jaime I Award in Environmental Sciences this year. I was surprised with the decision of the jury during my stay in Brazil during this year’s Ciência Sem Fronteiras stay. It was great to have many, many messages with support and congratulations from many colleagues. My sincere thanks to all them!

I’m very happy with the award, as it aids supporting conservation efforts in the natural areas where I do my field work: Cazorla, Doñana, Alcornocales, Islas Canarias.

How do furgivorous birds build-up their fruit meals?

This is the third part of a trilogy of papers dedicated to understanding the evolution of fruit colors and visual signals evolved by plants to attract animal mutualists. The paper is now available online at the Proceedings of the Royal Society, Biology website.

Theory predicts that trade among mutualists requires high reliability. Here, we show that moderate reliability already allows mutualists to optimize their rewards. The colours of Mediterranean fleshy-fruits indicate lipid rewards (but not other nutrients) to avian seed dispersers on regional and local scales. On the regional scale, fruits with high lipid content were significantly darker and less chromatic than congeners with lower lipid content.

Sylvia atricapillaSylvia borin

On the local scale, two warbler species (Sylvia atricapilla and Sylvia borin, above) selected fruit colours that were less chromatic, and thereby maximized their intake of lipids—a critical resource during migration and wintering.

PRSB 1

Figure. The trade of resources characterizing mutualistic interactions leads to multiple, repeated interactions among individual producers and consumers. For example, birds use visual information to decide which fruits to consume. Two individual birds combine different fruit species in their meals during a short feeding bout (t0 − t1), along their foraging sequence, in which they visited different fruiting plants. M1–M4 indicate the composition of four meals, i.e. the number of fruits consumed and their species identity, different fruits with different colours. We analyzed the combination of colors in field-sampled fruit meals in relation to the nutrient composition and food “reward” obtained by the birds. Birds used markedly non-random combinations of colors in their meals, indicating a significant choice of fruit meals maximizing energy intake.

In a passage and wintering area in SW Spain where I intensively studied these birds, the two warbler species consistently selected fruit color combinations that were significantly less chromatic, evidencing the use of color as a cue of nutrient rewards during short feeding bouts. Being extremely dependent on fleshy fruits during migration and wintering, these warblers use a very diverse set of fruit species to build-up reserves required for long-distance flights (garden warbler) or winter survival (blackcap).

It is amazing how selective were these birds in their choice of fruits. Even in a short feeding bout blackcaps can ingest up to seven different fruit species. I used analyses of fecal pellets, identifying not only seeds, but also fruit skins in the remains using a microscope, which enabled me to identify the number of different fruit species consumed during a short feeding bout. The fruit meals thus combine a varied assortment of flavors, pulp types, etc. The warblers have a very short gut passage time (16 moon on average- and up to 40 min), so that a sample of faecal material indicates the previous choices of fruits made by the bird, immediately before capture. I used mist-netted birds that were released after capture.

Warblers need to maintain a high throughput of fruits when relying on fruit food because fleshy fruits are a quite “diluted” type of food: not only they are rich in water, quite succulent, but they also have indigestible seeds that occupy very valuable space within the bird’s gut. The birds need to process all this stuff very rapidly in order to get enough “reward”. In turn this is good for the plant because the seeds are readily dispersed away from the mother plant. This is a mutualistic interaction driven by the visual cues used by the birds.

Our results indicate that mutualisms require only that any association between the quality and sensory aspects of signallers is learned through multiple, repeated interactions. Because these conditions are often fulfilled, also in social communication systems, we contend that selection on reliability is less intense than hitherto assumed. This may contribute to explaining the extraordinary diversity of signals, including that of plant reproductive displays.

Updated dataset on fruit colors in Dryad

  I’ve updated our dataset on fruit colors that we used in the Journal of Evolutionary Biology paper. The full metadata is here, in the Dryad open-source repository. You can find this and other datasets also in the web page.

Starting fieldwork in Teno Bajo

  Starting fieldwork in Teno Bajo: “ We (Alfredo, Néstor and myself) are this week with field work in Teno Bajo (Teneriffe), finishing georreferencing and sampling of orijama (Neochamaelea pulverulenta) plants in the study plots. The work is going fine in this spectacular site. We study seed dispersal by the Gallotia endemic lizards to analyze the consequences of this specialized dispersal system on the genetic structure of the plant.” (Via Weblog de Pedro.)

New papers

Forthcoming papers

New papers, to be published later this year, now in press include:
– Rodríguez-Sánchez, F., Hampe, A., Jordano, P. and Arroyo, J. 2010. Past tree range dynamics in the Iberian Peninsula inferred through phylogeography and palaeodistribution modelling: A review. Review of Palaeobotany and Palynology 00: 000-000. May 2010. doi:10.1016/j.revpalbo.2010.03.008

– Verdú, M., Jordano, P. and Valiente-Banuet, A. 2010. Temporal rearrangements in the phylogenetic structure of plant facilitation networks. Journal of Ecology 00: 000-000. August 2010. [DOI: 10.1111/j.1365-2745.2010.01731.x]

– Olesen, J.M., Bascompte, J., Dupont, Y.L., Elberling, H. and Jordano, P. 2010. Missing and forbidden links in mutualistic networks. Proceedings of the Royal Society of London Series B-Biological Sciences, 00: 000-000. [doi: 10.1098/rspb.2010.1371]

Last papers

Last papers: “Our last papers have appeared in Molecular Ecology Resources, dealing with the description of new DNA microsatellite markers for Frangula alnus and Rhamnus alaternus (Rhamnaceae), two species we study in Los Alcornocales area. The next related paper will describe the markers for Neochamaelea pulverulenta (Cneoraceae). These works are largely the result of efforts by our technicians JuanMi Arroyo and Cristina Rigueiro.”

(Via Weblog de Pedro.)