Species Interactions Important in determining – population dynamics community composition landscape spatial pattern ecosystem function T. Kittel, W. Bowman Univ of Colorado

General Categories Assigned by effect on the two individual organisms interacting: +, + = mutualismN 2 fixation, mycorrhizae +, 0 = commensalismNurse plants –, 0/+ = amensalismAllelopathy –, + = parasitism herbivory / predation –, – = competitionIntra & interspecific Think about these interactions in the context of species geography! Can be more complicated than direct interactions of 2 individuals  mediated through a 3 rd individual or species soil microbes, herbivores influence competitive interactions

A. Mutualism ( +, +) Plant - Microbe Mycorrhizae N–fixation Lichen Rhinoceros Hornbill eating Strangler Fig fruits, Borneo Mucuna holtonii, Central America Plant - Animal Pollination Insects Birds Hummingbirds Bats Fruit dispersal Defense Ants Azteca Ants on Cecropai, Panama

“The Forgotten Pollinators” Rufous Hummingbird Monarch Butterfly White-winged Dove Arizona-Sonoran Desert Museum Lesser Long-nosed Bat “Nectar corridors” Sequence of flowering plants Long–distance migratory pollinators Threatened – habitat loss Keystone species

moss v. lichen Atlantic Forest, Brazil B. Commensalism ( +,0) Plant-Plant 1) Vines 2) Epiphytes Bromeliads Orchids Cacti Ferns Lichen Moss Algae Staghorn fern

Exceptions – Commensalism goes  to Mutualism –  Lichen with cyanobacteria: N leaching, benefit to tree  goes bad –  Competition Strangulation Overtopping  Detrimental overburden Strangler fig

Pueraria montana var. lobata Kudzu – “the vine that ate the south” Introduced 1876 from Asia Planted for soil conservation 1930’s Oriental Bittersweet Vine, introduced from e. Asia Invasion in eastern US Celastrus orbiculata

2) Nurse plants Saguaros under Palo Verde Desert annuals under shrubs A. Commensalism – continued Piñon pine under Sagebrush

Plant - animal commensalism – Habitat Oropendola nests, Roraima Brazil Titi monkey, São Paulo Brazil Red-footed Booby in Mangrove Galápagos Is. Iran Jaya's People of the Trees nesting roosting hunting for other animals shelter from other animals

C. Amensalism ( –, 0 /+ ) Allelochemical Interactions Plant–Plant Allelopathy Larrea tridentata - Creosote Plant–Animal Herbivory defenses Big sagebrush with native bunchgrasses growing under canopy  Difficult to show in field Plant–Decomposer Litter composition  soil pH  soil biota: Conifer  low pH  fungi favored, Temperate Deciduous  neutral  bacteria Plant leakage of compounds detrimental to soil biota

D. Parasitism ( –,+ ) Dodder (Cuscuta) – stem parasite no chlorophyll = holoparasite

Coral root orchid - Corallarhiza maculata root parasite on pines

Mistletoe – stem parasite differing degrees of chlorophyll with chlorophyll = hemiparasite w/o  holoparasite Arceuthobium americanum Carpellate plant on Pinus contorta Arceuthobium cyanocarpum Staminate plant (left) and carpellate plant (right) on Pinus ponderosa Dwarf mistletoe – holoparasite

Broadleaf (Hairy) mistletoe - hemiparasite Phoradendron tomentosum on hackberry (Celtis laevigata), preferred host

More hemiparasites: Indian paintbrush – Castilleja spp. Root parasite

Inference of species interactions on the landscape If species interactions are important to plant species – Should be reflected in the spatial patterns of individuals (inter and intraspecific) if mutualisms among plant species occur, should be a positive association  they should occur closer together (clumped) than predicted by chance (random)

Landscape spatial patterning (con’t) if amensalism occurs, should be pushed away from each other  giving an even distribution Larrea tridentata - Creosote

Landscape spatial patterning (con’t) Under competition – competitive exclusion leads to range separation niche partitioning Non-overlapping geographic ranges of five species of large kangaroo rats

Within–canopy distribution Amazonian tree –  The long roots dangling from the crown probably belong to Philodendrons  On the middle and upper branches cluster groups of orchids, bromeliads, and ferns – including staghorn fern  Low on the trunk are Arums & Philodendrons with heart-shaped leaves

Keystone species Presence of a species determines community structure disproportionately to population size

Summary – Species Interactions  Plants and animals engaged in interactions with wide range of other taxa  Positive, detrimental, or neutral effects of one species on another  Reflected in spatial patterns – random vs. even vs. uniform  Reflected in community structure – Keystone species