GEOGRAPHIC PATTERNS IN PLANT–POLLINATOR MUTUALISTIC NETWORKS

Recent reviews of plant-pollinator mutualistic networks showed that gen- eralization is a common pattern in this type of interaction. Here we examine the ecological correlates of generalization patterns in plant-pollinator networks, especially how interaction patterns covary with latitude, elevation, and insularity. We review the few published anal- yses of whole networks and include unpublished material, analyzing 29 complete plant- pollinator networks that encompass arctic, alpine, temperate, Mediterranean, and subtrop- ical-tropical areas. The number of interactions observed (I) was a linear function of network size (M) the maximum number of interactions: ln I 5 0.575 1 0.61 ln M; R 2 5 0.946. The connectance (C), the fraction of observed interactions relative to the total possible, decreased exponentially with species richness, the sum of animal and plant species in each community (A 1 P): C 5 13.83 exp(20.003(A 1 P)). After controlling for species richness, the residual connectance was significantly lower in highland (.1500 m elevation) than in lowland networks and differed marginally among biogeographic regions, with both alpine and trop- ical networks showing a trend for lower residual connectance. The two Mediterranean networks showed the highest residual connectance. After correcting for variation in network size, plant species were shown to be more generalized at higher latitude and lowland habitats, but showed increased specialization on islands. Oceanic island networks showed an im- poverishment of potential animal pollinators (lower ratio of animal to plant species, A : P, compared to mainland networks) associated with this trend of increased specialization. Plants, but not their flower-visiting animals, supported the often-repeated statements about higher specificity in the tropics than at higher latitudes. The pattern of interaction build- up as diversity increases in pollination networks does not differ appreciably from other

[1]  Kamaljit S. Bawa,et al.  Plant-Pollinator Interactions in Tropical Rain Forests , 1990 .

[2]  R. Reader.  Competitive relationships of some bog ericads for major insect pollinators , 1975 .

[3]  C. Herrera,et al.  Floral Traits and Plant Adaptation to Insect Pollinators: A Devil’s Advocate Approach , 1996 .

[4]  Jens M. Olesen,et al.  The structure of a high latitude plant‐flower visitor system: the dominance of flies , 1999 .

[5]  P. Feinsinger.  Approaches to nectarivore - plant interactions in the new world , 1987 .

[6]  Neo D. Martinez.  Artifacts or Attributes? Effects of Resolution on the Little Rock Lake Food Web , 1991 .

[7]  Makoto Kato,et al.  Insect-flower Relationship in the Temperate Deciduous Forest of Kibune, Kyoto : An Overview of the Flowering Phenology and the Seasonal Pattern of Insect Visits , 1990 .

[8]  P. Legendre,et al.  MODELING BRAIN EVOLUTION FROM BEHAVIOR: A PERMUTATIONAL REGRESSION APPROACH , 1994, Evolution; international journal of organic evolution.

[9]  H. Nagamasu,et al.  Pollination biology in a lowland dipterocarp forest inSarawak, Malaysia. I. Characteristics of the plant-pollinator communityin a lowland dipterocarp forest. , 1998, American journal of botany.

[10]  J. Olesen,et al.  Invasion of pollination networks on oceanic islands: importance of invader complexes and endemic super generalists , 2002 .

[11]  C. Michener.  Bees of Panama , 1954 .

[12]  Kamaljit S. Bawa,et al.  La Selva: ecology and natural history of a neotropical rain forest. , 1995 .

[13]  S. Hall,et al.  Food-web patterns : lessons from a species-rich web , 1991 .

[14]  Juan J. Armesto,et al.  COMMUNITY STUDIES IN POLLINATION ECOLOGY IN THE HIGH TEMPERATE ANDES OF CENTRAL CHILE. I. POLLINATION MECHANISMS AND ALTITUDINAL VARIATION , 1982 .

[15]  Richard B. Primack,et al.  Insect pollination in the New Zealand mountain flora , 1983 .

[16]  Mary Percival,et al.  Floral Ecology of Coastal Scrub in Southeast Jamaica , 1974 .

[17]  Joel E. Cohen,et al.  Temporal Variation in Food Web Structure: 16 Empirical Cases , 1991 .

[18]  J. E. Cohen,et al.  Food webs and niche space. , 1979, Monographs in population biology.

[19]  J. Ollerton.  Reconciling Ecological Processes with Phylogenetic Patterns: The Apparent Paradox of Plant--Pollinator Systems , 1996 .

[20]  John A. Wiens,et al.  Species diversity in ecological communities: edited by Robert E. Ricklefs and Dolph Schluter University of Chicago Press, 1993. $105.00 hbk, $35.00 pbk (414 pages) ISBN 0 226 71822 0/0 226 71823 9 , 1994 .

[21]  Makoto Kato.  Plant-pollinator interactions in the understory of a lowland mixed dipterocarp forest in Sarawak , 1996 .

[22]  Makoto Kato,et al.  Flowering Phenology and Anthophilous Insect Community in the Cool-Temperate Subalpine Forests and Meadows at Mt. Kushigata in the Central Part of Japan , 1993 .

[23]  Steiner,et al.  Generalization versus specialization in plant pollination systems. , 2000, Trends in ecology & evolution.

[24]  J. Ollerton,et al.  Phenotype space and floral typology: towards an objective assessment of pollination syndromes , 2000 .

[25]  J. Thompson,et al.  The Coevolutionary Process , 1994 .

[26]  Robert K. Colwell,et al.  Community Organization Among Neotropical Nectar-Feeding Birds , 1978 .

[27]  G. Sugihara,et al.  Scale invariance in food web properties. , 1989, Science.

[28]  G. Polis,et al.  Complex Trophic Interactions in Deserts: An Empirical Critique of Food-Web Theory , 1991, The American Naturalist.

[29]  B. Hocking,et al.  Insect-flower associations in the high Arctic with special reference to nectar' , 1968 .

[30]  Javier Herrera,et al.  Pollination relationships in southern Spanisch Mediterranean shrublands , 1988 .

[31]  Makoto Kato,et al.  Insect-flower Relationship in the Primary Beech Forest of Ashu, Kyoto : An Overview of the Flowering Phenology and the Seasonal Pattern of Insect Visits , 1990 .

[32]  Pedro Jordano,et al.  Patterns of Mutualistic Interactions in Pollination and Seed Dispersal: Connectance, Dependence Asymmetries, and Coevolution , 1987, The American Naturalist.

[33]  Jan Bengtsson,et al.  CONFOUNDING VARIABLES AND INDEPENDENT OBSERVATIONS IN COMPARATIVE ANALYSES OF FOOD WEBS , 1994 .

[34]  Lars Chittka,et al.  Generalization in Pollination Systems, and Why it Matters , 1996 .

[35]  Duncan J. Watts,et al.  Collective dynamics of ‘small-world’ networks , 1998, Nature.

[36]  M. R. Dudash,et al.  Pollination 'principles' revisited: specialization, pollination syndromes, and the evolution of flowers , 2000 .

[37]  K. Gaston,et al.  Abundance-body size relationships: The area you census tells you more , 1996 .

[38]  B. G. Baldwin,et al.  Switch from specialized to generalized pollination , 1998, Nature.

[39]  J. Ollerton.  Pollination: Sunbird surprise for syndromes , 1998, Nature.

[40]  D. Schemske,et al.  Flowering Ecology of Some Spring Woodland Herbs , 1978 .

[41]  G. Sugihara,et al.  Effects of taxonomic and trophic aggregation on food web properties , 1997, Oecologia.

[42]  D. Snow,et al.  Feeding niches of hummingbirds in a Trinidad valley , 1972 .

[43]  Stanley Wasserman,et al.  Social Network Analysis: Methods and Applications , 1994 .

[44]  K. Gaston,et al.  Some Methodological Issues in Macroecology , 1998, The American Naturalist.

[45]  C. Herrera.  Variation in mutualisms : the spatio temporal mosaic of a pollinator assemblage , 1988 .

[46]  David W. Inouye,et al.  Pollination biology in the Snowy Mountains of Australia: Comparisons with montane Colorado, USA , 1988 .

[47]  Robert H. Whittaker,et al.  Evolution of Species Diversity in Land Communities , 1977 .

[48]  Makoto Kato,et al.  Flowering phenology and anthophilous insect community at a threatened natural lowland marsh at Nakaikemi in Tsuruga, Japan. , 1996 .

[49]  J. Gentle,et al.  Randomization and Monte Carlo Methods in Biology. , 1990 .

[50]  N. Ramírez.  Biologia de polinizacion en una comunidad arbustiva tropical de la Alta Guayana Venezolana , 1989 .

[51]  J. Roughgarden,et al.  Construction and Analysis of a Large Caribbean Food Web , 1993 .

[52]  Insect-flower Relationship in the Campus of Kyoto University, Kyoto : An Overview of the Flowering Phenology and the Seasonal Pattern of Insect Visits , 1990 .

[53]  Peter Yeo,et al.  Natural history of pollination , 1947 .