Mutualism Disruption Threatens Global Plant Biodiversity: A Systematic Review

Abstract

BackgroundAs global environmental change accelerates, biodiversity losses can disrupt interspecific interactions. Extinctions of mutualist partners can create “widow” species, which may face reduced ecological fitness. Hypothetically, such mutualism disruptions could have cascading effects on biodiversity by causing additional species coextinctions. However, the scope of this problem – the magnitude of biodiversity that may lose mutualist partners and the consequences of these losses – remains unknown.Methodology/Principal FindingsWe conducted a systematic review and synthesis of data from a broad range of sources to estimate the threat posed by vertebrate extinctions to the global biodiversity of vertebrate-dispersed and -pollinated plants. Though enormous research gaps persist, our analysis identified Africa, Asia, the Caribbean, and global oceanic islands as geographic regions at particular risk of disruption of these mutualisms; within these regions, percentages of plant species likely affected range from 2.1–4.5%. Widowed plants are likely to experience reproductive declines of 40–58%, potentially threatening their persistence in the context of other global change stresses.ConclusionsOur systematic approach demonstrates that thousands of species may be impacted by disruption in one class of mutualisms, but extinctions will likely disrupt other mutualisms, as well. Although uncertainty is high, there is evidence that mutualism disruption directly threatens significant biodiversity in some geographic regions. Conservation measures with explicit focus on mutualistic functions could be necessary to bolster populations of widowed species and maintain ecosystem functions.

The unnoticed effect of a top predator on complex mutualistic ecological interactions

“…For example, mutualistic disruptions can induce cascading effects on biodiversity, but they remain quite unknown in an ecological context (Aslan et al 2013), especially on islands. Disruptions of seed dispersal systems vary widely and have been described in several insular territories worldwide, such as the Atlantic Ocean (Canary Islands: Nogales et al 2005;López-Darias and Nogales 2008), the Mediterranean Sea (Balearic Islands: Traveset and Riera 2005;Rodríguez-Pérez and Traveset 2010), the Pacific Ocean (Tahiti: Spotswood et al 2012;Hawaii: Culliney et al 2012;Tonga: Meehan et al 2002;Galapagos Islands: Heleno et al 2013;Bonin: Kawakami et al 2009), or the Indian Ocean (Mauritius: Hansen and Müller 2009).…”

“…Disruptions of seed dispersal systems vary widely and have been described in several insular territories worldwide, such as the Atlantic Ocean (Canary Islands: Nogales et al 2005;López-Darias and Nogales 2008), the Mediterranean Sea (Balearic Islands: Traveset and Riera 2005;Rodríguez-Pérez and Traveset 2010), the Pacific Ocean (Tahiti: Spotswood et al 2012;Hawaii: Culliney et al 2012;Tonga: Meehan et al 2002;Galapagos Islands: Heleno et al 2013;Bonin: Kawakami et al 2009), or the Indian Ocean (Mauritius: Hansen and Müller 2009). However, most of them deal with primary seed dispersal processes in which (1) an introduced vertebrate directly interacts with fruits and seeds of native plant species, or (2) a legitimate disperser has become extinct (see reviews by Traveset and Richardson 2006;Aslan et al 2013). In addition, seed effectiveness (sensu Schupp 1993;Schupp et al 2010) of the native (legitimate dispersers) versus introduced species (disruptors) has not been considered in most of these studies.…”

Overfishing disrupts an ancient mutualism between frugivorous fishes and plants in Neotropical wetlands

“…The disruption of pollination and seed dispersal mutualisms directly affects plant reproductive success and threatens biodiversity (Aslan et al, 2013;Dirzo et al, 2014;Valiente-Banuet et al, 2015). The vast majority of plants rely on animals to disperse their genes and progeny (Jordano, 2000;Ollerton et al, 2011).…”

“…Local extinction of large frugivores can even induce rapid evolutionary changes in seed size (Galetti et al, 2013). A burgeoning body of work evaluates the ecological repercussions of hunting frugivores (Aslan et al, 2013), but neglects the largest clade of vertebrates: fish.…”

An improved method for chloroplast genome sequencing in non-model forest tree species

“…So far, more than 300 complete chloroplast genome sequences from angiosperm species, covering a wide range of taxa, have been deposited at NCBI (http://www.ncbi.nlm.nih.gov/genomes/ GenomesGroup.cgi?taxid=2759&opt=plastid). However, plant species whose cp genomes have been sequenced represent only a tiny proportion (0.1 %) of all existing angiosperms (Aslan et al 2013). Prior to 2006, the complete chloroplast genome sequences of no more than 10 species had been deposited with NCBI, whereas since 2010, the number of chloroplast genomes reported has increased exponentially ( Fig.…”