Mutualism & Commensalism

Photo of hawk moth potentially pollinating Dianthus from Wikimedia Commons

Facilitation – in other words, “+” means benefits outweigh costs

Commensalism = +/0Mutualism = +/+

Positive Interactions

Photo of hawk moth potentially pollinating Dianthus from Wikimedia Commons

What might the benefits and costs be to each partner in a pollination mutualism?

Obligate – not optional, e.g., fig - fig waspFacultative – optional, e.g., fig - seed disperser

Obligate vs. Facultative Mutualisms

Fig & its pollinating fig waspsFig & one of its many seed-dispersers

(in this case a frugivorous bat)

Photo of fig & fig wasps from http://www.zoology.ubc.ca;photo of bat & figs from http://www.sserc.org.uk/wwwroot2/members/Photos/Plants/seed%20dispersal/Menu.htm

Types of Benefits to Mutualists

Photo from Wikimedia Commons

Service MutualismsOne partner receives an ecological service from the other – e.g., pollination,

seed dispersal, or defense against herbivores, predators, or parasites

E.g., ant - bullhorn acacia

Types of Benefits to Mutualists

Photo from Wikimedia Commons

Habitat MutualismsOne partner obtains shelter, a place to live, or favorable habitat from the other

E.g., alpheid shrimp - goby symbiosis

Trophic MutualismsOne partner receives energy or nutrients from its partner

E.g., mychorrizae – plant root - fungus symbiosis

Types of Benefits to Mutualists

Photomicrograph from Wikimedia Commons

Each mutualistic partner seeks to gain benefit from the other(just like a parasite seeks to gain benefit from a host);

this can create conflicts

Mutualists Are Not Altruists

Photo of yucca moth from: http://www.cals.ncsu.edu/course/ent425/images/pollinators_gallery/pages/06_yucca_moth_jpg.htm; Harms’s photo of yuccas in White Sands Nat’l. Park, NM; Cain, Bowman & Hacker (2014), Fig. 15.16, after Pellmyr & Huth (1994) Nature

Yuccas selectively

abort flowers into which too many eggs are

laid

Cheaters can be Penalized or Sanctioned

A

B C

Plant can penalize fungus (for poor P delivery) with low C delivery

Split-plate design: (A) plant roots labeled with 14C; (B) mycorrhizal fungus without P;

(C) mycorrhizal fungus with P (either 35 M or 700 M)

Kiers et al. (2011) Science

Cheaters can be Penalized or Sanctioned

Split-plate design: (A) fungal hyphae labeled with 33P; (B) roots with no access to sucrose;

(C) roots with access to sucrose (either 5 mM or 25 mM)

A

B CFungus can penalize plant

(for poor C delivery) with low P delivery

Plant can penalize fungus (for poor P delivery) with low C delivery

Split-plate design: (A) plant roots labeled with 14C; (B) mycorrhizal fungus without P;

(C) mycorrhizal fungus with P (either 35 M or 700 M)

Title of the project:

“Reciprocal rewards stabilize

cooperation in the mycorrhizal

symbiosis”

Kiers et al. (2011) Science

Notorious filamentous fungal pathogen, Colletotrichum magna, causes anthracnose disease in cucurbits

Member of a large clade of pathogens capable of infecting the majority of agricultural crops worldwide

Mutualisms Can Evolve From Other Types of Species Interactions

Original research from Freeman & Rodriguez (1993) Science;photo of anthracnose on cucumber leaf fromhttp://urbanext.illinois.edu/hortanswers/detailproblem.cfm?PathogenID=128

The heart-warming tale of a reformed parasite

Infection occurs when spores adhere to host tissue, enter a cell, and subsequently grow through the host leaving a trail of necrotic tissue

Mutualisms Can Evolve From Other Types of Species Interactions

The heart-warming tale of a reformed parasite

“Path-1” = single-locus mutant of C. magna that spreads throughout the host (albeit more slowly) without necrosis & is a non-sporulating endophyte

Plants infected with Path-1 were protected from the wild-type & were immune to an unrelated pathogenic fungus, Fusarium oxysporum

Path-1 may induce host defenses against pathogens or may outcompete other fungi

Considerable potential exists to tailor endophytes as biocontrol agents; an example of Darwinian Agriculture

Original research from Freeman & Rodriguez (1993) Science;photo of cucurbits grown without (left) and with (right) Path-1 C. magna, both in the presence of Fusarium, fromhttp://wfrc.usgs.gov/research/contaminants/STRodriguez4.htm

Species Interactions Can Vary Geographically, Temporally, or in Other Context-Dependent Ways

Cattail facilitated small-flowered forget-me-not at low soil temp. (possibly owing to

soil aeration)

Photo of cattail from Wikimedia Commons; Cain, Bowman & Hacker (2014), Fig. 15.9, after Callaway & King (1996) Ecology

Species Interactions Can Vary Geographically, Temporally, or in Other Context-Dependent Ways

Cattail facilitated small-flowered forget-me-not at low soil temp. (possibly owing to

soil aeration)

Cattail competed with small-flowered forget-me-not at

high soil temp.

Photo of cattail from Wikimedia Commons; Cain, Bowman & Hacker (2014), Fig. 15.9, after Callaway & King (1996) Ecology

Daniel H. Janzen e.g., ant-acacia mutualism

*When is it Coevolution?Reciprocal adaptive evolution in each of 2 interacting species

in response to adaptations in the other species

Photo of Janzen from http://www.fbbva.es/TLFU/tlfu/ing/microsites/premios/fronteras/galardonados/2011/ecologia.jsp; image of “Darwin’s hawk moth” pollinating its Malagasy orchid from http://botany.si.edu/events/sbsarchives/sbs2008;*original idea from Janzen (1980) Evolution

“Darwin’s hawk moth”potentially pollinating its

Malagasy orchid

Positive interactions can influence individuals, populations, interactions between species, communities

& ecosystems

Photomicrograph from Wikimedia Commons

Zoxanthellae = unicellular algal protist symbionts with corals

A world without zoxanthellae would be a world without most shallow-water corals

Imagine a world without corals