{"id":230072,"date":"2017-01-13T15:54:39","date_gmt":"2017-01-13T17:54:39","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/en\/?p=230072"},"modified":"2017-01-13T15:54:39","modified_gmt":"2017-01-13T17:54:39","slug":"great-gardeners-2","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/great-gardeners-2\/","title":{"rendered":"Great gardeners"},"content":{"rendered":"

\"Megafauna_231_ILUSTRA_AF-edit\"elisa carareto<\/span><\/a>Published in may 2015<\/a><\/em><\/p>\n

Until some 10,000 years ago, giant ground sloths, mastodons and wild horses populated the South American landscape. The extinction of these mammals, known as Pleistocene megafauna, whose weight could reach several tons, may have significantly affected the vegetation of the Brazilian Pantanal wetland, according to a paper published in the journal Oecologia<\/em> in August 2014. Although the flora that depended on Pleistocene megafauna as seed dispersers have not disappeared (there are other dispersers, including humans), they may have become less abundant and may occupy smaller areas than in the past. \u201cOur proposal aimed to open the way for an ecological approach that could be used to observe specific relationships that had been established between animals and plants to better understand what happened when these giants left the scene,\u201d explains Mathias Pires of the Department of Ecology at the University of S\u00e3o Paulo Biosciences Institute (IB-USP).<\/p>\n

Pires was inspired by the work of the Brazilian researcher Camila Donatti during her doctoral studies at Stanford University, in collaboration with the group led by Mauro Galetti, an ecologist at S\u00e3o Paulo State University (Unesp) at Rio Claro campus<\/em>, which was published in the journal Ecology Letters<\/em> in 2011.<\/p>\n

Donatti studied animals in the Pantanal wetland \u2013 from fish to mammals \u2013 and characterized their seed dispersal habits. \u201cDonatti\u2019s approach simplifies inter-species interactions into a local dataset. Using this approach, in which we represent species by dots and their interactions by lines, we can extract data on how the organisms are interconnected,\u201d Pires explains. \u201cFor example, we know that a certain animal consumes the fruits and disperses the seeds of plants 1, 2 and 3, but species B can only disperse plant 1, and species C scatters only 2 and 3.\u201d<\/p>\n

During his doctoral studies under the supervision of Paulo Guimar\u00e3es, Pires took on the challenge of researching how that same network of interactions might have worked in the past. Using data on fossils found in the region, he juxtaposed the present-day animals of the Pantanal with five species of megafauna that inhabited the biome long ago. These included giant ground sloths, mastodons and a relative of present-day llamas. Pires recalled that these large animals are described in scientific literature as good plant dispersers by virtue of at least two distinctive features: because they were quite large and their diet included a variety of fruits, they ingested large seeds that smaller animals couldn\u2019t scatter. Furthermore, they could traverse long distances, and because they digested their food slowly, the seeds germinated in places far from the mother plant.<\/p>\n

As for the plants, Pires made a list of 10 species, specifically those whose seeds are still scattered by mammals today, such as pequi fruit, jatob\u00e1 (Brazilian cherries) and some palm species. With the appropriate substitutions and adaptations, he then employed simulations, mathematical models, computers and statistics. \u201cThe idea was to observe the present-day network and investigate how it might have been in the past.\u201d<\/p>\n

Yesterday and today<\/strong>
\nPires highlights another finding of the study: in the networks he reconstructed, the seed-disperser roles played by megafauna were distinct and well-defined, in that large animals scattered larger seeds, and small animals dispersed the small ones. In keeping with the findings of Donatti\u2019s study, that distinction no longer exists. \u201cWithout the mastodons and giant ground sloths, the larger fruits have lost their principal dispersers. Tapirs, coatis and howler monkeys, for example, probably played a secondary role in seed dissemination during the Pleistocene, but today, they are key agents of large-seed dispersal,\u201d he explains.<\/p>\n

This look at the past indicates that the absence of megafauna may have had a significant impact on the vegetation of the Pantanal, as shown in a study led by Galetti. The paper, published in 2013 in the journal Science<\/em>, suggests that in areas of the Atlantic Forest, where large birds have been extinct for more than 50 years, populations of palm trees produce only small fruit; in contrast, in better-preserved areas that have larger birds, there are still fruits of various sizes. \u201cThe same thing may have happened following the extinction of the large mammals of the past. In addition, plants that lose their seed dispersers end up confined to smaller regions, and the loss of dispersers hinders gene flow between populations. In the long term, this situation can reduce the genetic diversity of populations and lower their resistance to pests, for example,\u201d he adds.<\/p>\n

In Galetti\u2019s opinion, this finding suggests that there is a need to responsibly consider the idea of introducing other mammals, such as horses and pigs, into the Pantanal to serve as dispersers. \u201cPerhaps some of these species can even help restore the losses,\u201d he surmises. Pires makes a further point: his work also provides an opportunity for reflection about the present-day biodiversity crisis. In his view, we need to understand ecological interactions in order to find ways to mitigate the consequences of the potential loss of large species.<\/p>\n

The biologist, eager to add more data to this scenario, now plans to do a comparative study of other biomes so as to observe the effects of species extinction on each one. \u201cCould the absence of tapirs in the Atlantic Forest have the same effects as in the Cerrado savannah?\u201d he wonders. He also plans to do a quantitative comparison of the effectiveness of some animal species in the task of seed dispersal, again with an eye to the past. \u201cWe are developing mathematical models to observe how indispensable a giant ground sloth might have been in carrying seeds long distances, compared to a tapir or a peccary of today, for example,\u201d the researcher says in closing.<\/p>\n

Projects<\/strong>
\n1.<\/strong> Structure and evolutionary dynamics in mutualistic networks (n\u00ba 2009\/54422-8<\/a>); Grant mechanism<\/strong> Young Investigators Awards Program; Principal investigator <\/strong>Paulo Roberto Guimar\u00e3es Junior (USP); Investment<\/strong> R$161,960.08 (FAPESP).
\n2.<\/strong> Plant attributes in the Pantanal seed dispersal network: consequences on spatial and demographic patterns (n\u00ba 2008\/10154-7<\/a>); Grant mechanism<\/strong> Regular Research Grant; Principal investigator Mauro Galetti Rodrigues (Unesp); Investment<\/strong> R$117,963.58 (FAPESP).<\/p>\n

Scientific article<\/em>
\nPIRES, M. M. et al.<\/em> Reconstructing past ecological networks: the reconfiguration of seed-dispersal interactions after mega-faunal extinction<\/a>. Oecologia<\/strong>. V. 175, No. 4, p. 1247-56. Aug. 2014.<\/p>\n","protected":false},"excerpt":{"rendered":"Mathematical models reconstruct the seed-dispersing role by now-extinct animals","protected":false},"author":18,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[159],"tags":[219,224],"coauthors":[109],"class_list":["post-230072","post","type-post","status-publish","format-standard","hentry","category-science","tag-computation","tag-ecology"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/230072","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/18"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=230072"}],"version-history":[{"count":0,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/230072\/revisions"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=230072"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=230072"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=230072"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=230072"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}