Coevolution: The joint evolution of two species with close ecological relationships -- evolution of each is partly dependent on the other -- includes parasite-hosts, mutualisms

vertebrates (social parasitism) Parasites include: viruses bacteria fungi invertebrates vertebrates (social parasitism) Many are highly specialized to only one host species e.g, bird lice, botflies Plant mite Human head lice

Host defenses against parasites --Biochemical (e.g., antibodies) --tissue growth to contain parasite (e.g., galls)

To eradicate parasites -- gene-for-gene response -- multiple defenses at once (not really possible) -- turn it into a mutualism

Mutualisms: coevolved systems where two species interact to the benefit of both -- e.g., Rhizobium, Mycorrhiza -- symbiotic and nonsymbiotic -- obligate and facultative Landmark paper on coevolution and mutualism in ecology: Erhlich, Paul and Peter Raven. 1965. Butterflies and plants: a study in coevolution. Evolution 18: 586-608.

Social parasitism in birds cuckoos cowbirds some ducks 2 Brown-headed Cowbird eggs in a Blue-winged Warbler's nest warbler nest with two cowbird eggs Brown-headed cowbird

parasitism to mutualism Oropendolas and Cowbirds parasitism to mutualism

-- symbiotic and nonsymbiotic Landmark paper on coevolution and mutualism in ecology: Erhlich, Paul and Peter Raven. 1965. Butterflies and plants: a study in coevolution. Evolution 18: 586-608. -- symbiotic and nonsymbiotic -- obligate and facultative

Pine cone seeds and crossbills

Ants and acacia trees

Dodo Mauritius Island Calvaria trees Nonsymbiotic obligate mutualism (for tree)

Honey badger and honeyguide: a nonsymbiotic facultative mutualism

Mutualisms are not always ideal -- not always a ‘happy’ relationship -- e.g., yucca moths pollinate plants, larvae feed on seeds -- too many larvae, flower dies and both species lose out -- puts constraints on fecundity

Now know that mutualisms and other co-evolved systems are common in nature -- functional links above ground to below ground -- nutrient cycling and ecosystem function often dependent on these relationships -- more discovered all the time Tree shrew and pitcher plant in Borneo Wax from plant, nitrogen in feces from shrew Pitcher plants and tree shrews have formed a relationship of mutual benefit: the shrews feed on the plant’s wax and defecate into its convenient “lavatory”, so providing the plant with 60 to 100 per cent of its nitrogen needs.

Pollination Ecology

Hummingbirds: generalists and specialists

Mutualisms: last word --not always a ‘happy’ relationship --e.g., yucca moths on yucca plants --constraints on fecundity