ANT 154BN-13 Niche theory and interspecfic competition

ANT 154BN-13 Niche theory and interspecfic competition -...

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Unformatted text preview: ANT 154BN Lecture #13: Niches & inter-specific competition 1 17 Feb 2011 Community ecology 13: 14: 15: 16: Niche theory & inter-specific competition Primate community structure Biogeography and diversity: comparing communities Diversity: patterns and processes 2 Niche theory & inter-specific competition 1. Niche theory 2. Competition among primate species 3. Competition with other species Niche theory & inter-specific competition >1. Niche theory 2. Competition among primate species 3. Competition with other species The Niche environmental factors that influence the growth, survival, and reproduction of a species the limits, for all important environmental features, within which individuals of a species can survive, grow, and reproduce how a species makes a living; its role in the community, the environmental conditions it tolerates, the important resources it needs to survive, and its ways of obtaining those resources Anolis insolitus, twigs Anolis garmani, large tree crowns Anolis chlororcyanus, tree trunk-crown Anolis cybotes, trunk-ground Competitive exclusion principle no two organisms can occupy exactly the same niche Niche theory: resource partitioning, niche overlap, and inter-specific competition The “Hutchinsonian” Niche niche as “an n dimensional hypervolume, enclosing the complete range of conditions under which an organism can reproduce itself” In theory, all variables relevant to the life history of an organism must be included. G. E. Hutchinson A, C A use of second dimension F D E B AB B C F E E, F D CD use of first dimension Fundamental niche: the niche an organism would occupy in the absence of competition, predation, and other biotic interactions that limit the organism. An abstraction. Realized niche: the niche an organism actually occupies in a given environment. Possibly real, but very hard to measure in real life. Fundamental niche Realized niche Niche Partitioning and Diversity As a new area is colonized, very little competition, realized niches similar to fundamental niches As the habitat fills up, more competition, realized niches become smaller and more specialized species sorting: species that are out-competed go extinct Compression hypothesis species poor community species rich community species B species A species A species C habitat types species B species D species E species F species G species B foods within habitat foods within habitat after MacArthur & Wilson 1967 Utility of the niche concept Niches are theoretical abstractions Useful in conceptualizing ecological concepts Most organisms partition niche space based on: habitat type occupied resources used (food, nest sites, etc.) when resources used * Competitive exclusion principle no two organisms can occupy exactly the same niche Ecological time scale Other finch species’ dietary overlap with medium ground finch differs by season % dietary overlap low food availability high FBF and niche differentiation A, C F D E B D E B A B C,D E F A C F use of fallback foods use of preferred food resources Evolutionary time scale Anolis lizards Schoener (1968) Character displacement Ghost of competition past? Ghost of competition past? Little evidence of character displacement ISLAND Petroica NICHE AND FORAGING sympatric allopatric BLACK T I 1 N=97 p e r c e n t of observations 1%) McLean et al. 1994 Asymmetric competition Asymmetric competition reduce food available to gibbons little effect on leaf monkeys leaf monkeys feed on unripe fruits gibbons feed on ripe fruits Overlap indices have important effects Overlap indices have important effects Species A number of observations Species B 15 ABBBBBCCCDDDDDE 10 AAAAAAABBC Items consumed in common ABC 100% (3/3) ABBC 40% (4/10) 27% (4/15) 60% (3/5) True overlap Niche theory & inter-specific competition 1. Niche theory >2. Competition among primate species 3. Competition with other species Competition “Competition is any use or defense of a resource by one individual that reduces the availability of that resource to other individuals” Ricklefs 2007 Inter-specific competition occurs when: 1. two or more species use the same resources 2. resources are limited in abundance or availability Potential primate responses to fruit scarcity • increase utilization of few remaining fruit resources predict: diets converge during fruit poor times, inter-specific competition intensifies • fallback on different food resources predict: diets diverge during fruit poor times Dietary overlap reduced during lean seasons % feeding time on chimpanzee foods Redtail monkeys r = 0.72, p < 0.01 Blue monkeys r = 0.85, p < 0.001 fruit availability Kibale primates, Wrangham et al. 1998 Dietary overlap reduced during lean seasons 100 % species paris 23 pairs of sympatric primates 0 low fruit period seasonal diet divergence high fruit period Waser 1987 dietary overlap with gibbons. The top row of graphs shows data for vertebrate species (abbreviations follow Fig ow shows data for vertebrate families (abbreviations follow Figure 2). 1 1 1 1 Dietary overlap Dietary overlap Dietary overlap 0.8 0.6 0.8 0.6 0.4 0.2 0 LFP HFP 0.8 0.6 0.4 0.2 0 LFP HFP Dietary overlap 0.8 0.6 0.4 0.2 0 0.4 peat forest 0.2 0 LFP HFP LFP : Diet overlap between gibbons and other important vertebrate frugivores in non-peat forests. Explanation and FK KL OH RH ns as in Figure XY. 1 HFP Dietary overlap Dietary overlap Dietary overlap Dietary overlap Dietary overlap Dietary overlap LFP LFP LFP LFP LFP LFP LFP LFP PONGI 0 FK 1 CERCO 0 KL 1 BUCER 0 OH 1 MEGAL 0 RH 1 MAST MAST MAST verlap verlap verlap MAST HFP HFP HFP HFP 0.8 0.6 0.8 0.6 0.8 0.6 0.8 Marshall et al. 2009 0.6 verlap LFP LFP HFP HFP HFP HFP 0.8 1 0.6 0.8 0.4 0.6 0.2 dryland 0.4 0 0.2 forest 0.8 1 0.6 0.8 0.4 0.6 0.2 0.4 0 0.2 0.8 1 0.6 0.8 0.4 0.6 0.2 0.4 0 0.2 Dietary overlap Dietary overlap leaf monkeys 1 orangutans 1 1 0.8 1 0.6 0.8 0.4 0.6 0.2 0.4 0 0.2 LFP Potential primate responses to fruit scarcity • increase utilization of few remaining fruit resources predict: diets converge during fruit poor times, competition intensifies X rare • fallback on different food resources predict: diets diverge during fruit poor times √ common squirrels, long-tailed macaques, and Figure 8: Diameter of feeding trees of gibbons and their major competitors. The boxplots depict the diameter of feeding trees for each vertebrate taxon, showing the median (black horizontal lines), interquartile range (gray boxes), extent of points within 1.5 of the quartile range (upper and lower range lines), and outliers (points). Red leaf monkeys (PR) and orangutans (PP) fed in significantly larger trees than did all other taxa (* Tukey-Kramer HSD q> 2.82, p < 0.05); the size of trees fed in by gibbons (HA) did not differ significantly from Prevost’s squirrel (CP), long-tailed macaques (MF), or rhinoceros hornbills (BR). Sample sizes for each taxon are given above initials. Gibbons feed in smaller trees than two major primate competitors * * 160 140 Size of feeding trees (cm dbh) 120 100 80 60 40 20 0 N= 30 CP CP 128 FK MF 48 GN HA 44 HB BR 46 KL PR 301 OH PP Prevost’s Long-tailed Squirrel macaque Gibbon Rhino hornbill Leaf monkey Orangutan Marshall et al. 2008 Lambert et al. 2004 Food hardness Redtail monkey (thiner enamel) Mangabey (thicker enamel) All years Drought years All years Drought years Young’s modulus, E MPa Fracture toughness, R J m-2 Hardness Toughness Orangutansefeedgoness of Confoods thansgibbons Fractur Tou hn tougher sumed Item =999 Wilcoxon, p=0.01 ,"#-'&"./0+&%1$.22/345678 <999 * ;999 7999 :999 9 ! " # $ % & '# $ ( )* * + $ Vogel et al. 2009 Orangutans ’feed dulharderit Consthan d Young s Mo on us Fru foods ume gibbons? : Wilcoxon, p=0.21 ,+&$%-./0+1&2&./304#5 9 8 7 6 ! "# $ % & '# $ ( )* * + $ But could not test: 1) Xylopia malayana 2) Mezzetia leptopoda 3) Blumeodendron kurzii Not consumed by gibbons and selected for by orangutans (Haag, 2007) Vogel et al. 2009 Niche theory & inter-specific competition 1. Niche theory 2. Competition among primate species >3. Competition with other species (c) Tim Laman rtant vertebrate frugivores in peat and non-peat forests. The y-axis lists percent of Figure 5: Overall diet overlap between gibbons and other y composition and the frequency of items in the diet). Black boxes and lines important vertebrate verlap with gibbon on 1000 randomly drawn diets. Open s of expected overlapowith gibbons baseddiets (a measure incorporating both dietary composition an indicate, respectively, the mean and upper and lower 95% 2), row of graphs shows data for vertebrate species (abbreviations follow Figurelimits of expected ove circles indicate observed dietary overlap with gibbons. The top row of graphs sh ns follow Figure 3). the bottom row shows data for vertebrate families (abbreviations follow Figure 3 Non-primate frugivores are potentially important competitors of gibbons 11 11 1 Dietary overlap Dietary overlap Dietary overlap NonPeat NonPeat Peat Peat 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 00 NonNonPeat Peat Peat Peat Dietary overlap Dietary overlap 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 00 0.8 0.6 0.4 0.2 0 NonPeat Peat eat NonPeat Peat PP CP Dietary overlap Dietary overlap 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 00 BR MF Dietary overlap Dietary overlap 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 00 PR 1 11 Prevost’s squirrel 11 Rhinoceros hornbill Dietary overlap oneat neat eat eat 0.8 0.6 0.4 0.2 0 oneat onneat eat neat eat eat eat Peat Peat Peat Peat Peat Peat Peat Peat PR PR CP SCIUR CERCO CERCO Dietary overlap Dietary overlap Dietary overlap 1 11 0.20.2 0.2 NonNonPeat NonPeat Peat Dietary overla Dietary overla Dietary overl 0.40.4 0.4 0.6 0.60.6 0.8 0.80.8 0.8 0.6 0.6 0.6 0.4 0.4 0.4 0.2 0.2 0.2 0 00 0 00 Non-primate frugivores are potentially important competitors of gibbons All squirrels NonNonPeat NonPeat Peat Peat Peat Peat Peat Peat Peat 0.8 PP MFPP PONGI BUCER BUCER 0.2 0.2 0.2 0 00 NonNonPeat NonPeat Peat Peat Peat Peat Dietary overlap Dietary overlap Dietary overlap 0.4 0.4 0.4 Dietary overla Dietary overla Dietary overl 1 11 0.6 0.6 0.6 0.8 0.8 0.8 0.6 0.6 0.6 0.4 0.4 0.4 0.2 0.2 0.2 0 00 All hornbills CERCO MEGAL MEGAL NonPeat NonNonPeat Peat Peat NonNonPeat NonPeat Peat Peat Peat Peat 0.8 BR PR BR Dietary overlap Dietary overlap Dietary overlap 0.2 0.20.2 0.4 0.40.4 0.6 0.60.6 0.8 0.80.8 0 00 1 11 Dietary overla Dietary overla Dietary overl NonPeat NonNonPeat Peat Peat 0.6 0.60.6 0.4 0.40.4 0.2 0.20.2 0 00 All barbets Peat Peat Peat Peat PP Dietary overlap 0.2 0 Non- Dietary overla 1 0 0.4 0.6 0.8 0.2 0.4 0.6 0.8 BUCER Non- The species with the highest degree of dietary overlap with gibbons was Prevost’s squirrel, (C a l l o s c i u r u s p r e v o s t i i : 51% overlap), followed by the three most common diurnal primates at CPRS: orangutans (P o n g o p y g m a e u s w u r m b i i: 4 9 %) , l o n g - t a i l e d macaques (Macaca fascicularis: 48%), and red leaf monkeys (P r e s b y t i s r u b i c u n d a r u b i d a : Important dietary overlap with gibbons three species should be considered co-equal and not significantly different. Other taxa with substantial dietary overlap (> 5%) with gibbons included bearded pigs (S u s b a r b a t u s ), binturong (Arctictis binturong) , and several species of hornbill (Bucerotiformes), barbets (Megalaimidae), bulbuls (Pynotidae), and squirrels (Sciuridae). Table 2: Important vertebrate competitors of gibbons at Gunung Palung. Order RODEN PRIMA PRIMA PRIMA BUCER RODEN BUCER PICIF ARTIO BUCER Family SCIUR PONGI CERCO CERCO BUCER SCIUR BUCER MEGAL SUIDA BUCER Latin name Callosciurus prevostii Pongo pygmaeus wurmbii Macaca fascicularis Presbytis rubicunda rubida Buceros rhinoceros Ratufa affinis Anorhinus galeritus Megalaima chrysopogon Sus barbatus Buceros vigil Common name Prevost's Squirrel Orangutan Long-tailed Macaque Red Leaf Monkey Rhinoceros Hornbill Giant Squirrel Bushy-crested Hornbill Gold-wiskered Barbet Bearded Pig Helmeted Hornbill Dietary overlap 50.5% 48.6% 48.2% 41.4% 30.7% 27.5% 17.3% 16.8% 15.5% 13.4% Table 2 lists the ten vertebrate frugivores with the highest degree of dietary overlap with gibbons. This analysis combines all fruit-feeding records from all habitat types. Family abbreviations are the same as used in Figure 3 We also examined whether forest type affected the intensity of feeding competition (as indexed by dietary overlap) between gibbons and other taxa. We limited this analysis to taxa to differences in sample sizes between peat and non-peat forests– actually all species showed Marshall, Cannonns Leighton 2009 the same patter & of overlap in peat and non-peat forests (Fig. 5). The family analysis revealed de feeding competition 14 Marshall et al.: Community-wide feeding competition een gibbons and other important vertebrate frugivores during low fruit periods (LFP) and high fruit Figure 6: Diet overlap between gibbons and other important vertebrate frugivores duri s. Explanation and abbreviations as in periods5. Figure (HFP) in peat forests. Explanation and abbreviations as in Figure 5. Little relationship between food availability and dietary overlap with non-primate competitors... 1 1 HFP Dietary overlap 1 1 1 HFP Dietary overlap 1 1 1 Dietary overlap Dietary overlap Dietary overlap Dietary overlap Dietary overlap 0.8 0.6 0.4 0.2 0 LFP HFP 0.8 0.6 0.8 0.6 0.8 0.6 0.8 0.6 0.8 0.6 0.8 0.6 0.4 0.2 0 HFP LFP HFP Dietary overlap Dietary overlap HFP LFP MAST LFP 0.8 0.6 peat forest feeding competition Marshall et 0.4 0.4 0.2 0 0.2 0 al.: Community-wide feeding competition 0.4 0.4 0.4 15 0.2 0 0.2 0 HFP LFP 0.4 0.2 0 0.2 Figure 7: Diet overlap between gibbons and other important vertebrate frugivores du n gibbons and other important vertebrate frugivores during low fruit periods (LFP), high fruit periods (HFP) and masts in non-peat forests. Explanation and abbreviations as in Figures 5 an rests. Explanation and abbreviations as in Figures 5 and 6. CP MF PR PP F PR PP BR 0 HFP LFP LFP LFP 1 1 1 1 Prevost’s squirrel 1 1 Rhinoceros1 hornbill LFP 1 LFP Dietary overlap Dietary overlap LFP Dietary overlap LFP Dietary overlap LFP HFP Dietary overlap HFP Dietary overlap MAST 0.8 1 0.8 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 LFP HFP LFP MAST 0.8 1 0.8 1 HFP HFP Dietary overlap Dietary overlap Dietary overlap LFP LFP Dietary overlap Dietary overlap Dietary overlap Dietary overlap 0.8 1 0.6 0.8 0.4 0.6 0.8 1 0.60.8 0.40.6 0.20.4 00.2 0 0.8 0.6 0.8 0.4 0.6 0.6 0.8 0.4 0.6 0.6 0.8 0.4 0.6 0.8 0.6 0.6 0.4 0.4 0.2 HFP LFP MAST LFP 0.6 0.4 0.2 0.20 dryland forest 0.4 0.2 0.2 0 0 LFP LFP HFP HFP MAST 0.4 0.4 0.2 0.2 0 0 0.4 0.2 0.2 0 0 0.2 MAST PR 1 CP PP MF BR PR MAST HFP HFP HFP NGI 0 SCIUR CERCO PONGI BUCER CERCO MEGAL HFP HFP 0.2 0 0 0.2 0 0 0 BUC P 1 1 1 1 1 1 Squirrel (Callosciurus prevostii, CP), Dog-faced Bat (Pteropus spp., PS), Fairy Bluebird (Irena puella, IP), Long-tailed Macaques (Macaca fascicularis, MF), Green Broadbill (Calyptomena viridis, CV), Bornean White-bearded Gibbon (Hylobates albibarbis, HA), Helmeted Hornbill (Buceros vigil, BV), Red Leaf Monkey (Presbytis rubicunda rubida, PR), Little Barbet (Megalaima australis, MA), Gold-whiskered Barbet (Megalaima chrysopogon, MC), Gaudy Barbet (Megalaima mystacophanes, MM), Red-crowned Barbet (Megalaima rafflesii, MR), Western Bornean Orangutan (Pongo pygmaeus wurmbii, PP), Longtailed Parakeet (Psittacula longicauda, PL), Giant Squirrel (Ratufa affinis, RA), Rhinoceros Hornbill (Buceros rhinoceros, BR), Little Green Pigeon (Treron capellei, TC), Tufted Ground Squirrel (Rheithrosciurus macrotis, TG), Wreathed Hornbill (Aceros undulatus, AU), and Wrinkled Hornbill (Aceros corrugatus, AC). ...because gibbons relatively unselective? % dietary identity CP HA PR BR PP # Independent feeding observations Marshall, Cannon & Leighton 2009 Take home messages 1. Diets of competitors tend to diverge during periods of resource scarcity (i.e., they use distinct fallback foods), but this patters in not universal. 2. Detection the effects of inter-specific competition, especially on the evolutionary scale, is difficult to do. 3. Both other primate species and non-primate vertebrates can be ecologically important competitors with primates. Question to ponder Due to an ever-increasing number of orangutan orphans being confiscated from the pet trade, there is substantial interest in surveying remaining Bornean forest fragments as potential release sites for ex-captive orangutans. One potential release site is a fairly large fragment of peat swamp forest in central Kalimantan that appears to contain an unusually high density of hornbills. As a consulting scientist, you have been asked to comment on potential conservation issues surrounding inter-specific feeding competition between orangutans and hornbills in this forest fragment. You dig around through the literature and find a single published study that quantifies dietary overlap between orangutans and hornbills. The study reports a 75% dietary overlap between the two species. The data in this study were well collected and effective sampling protocols were followed. Unfortunately, however, data were only collected for three months, during a period of relative fruit abundance. Furthermore, the published study was conducted in dryland forests in Sumatra. Question to ponder Two questions: a) Conservation managers have asked your expert opinion about whether competition with hornbills would adversely affect populations of released orangutans in the proposed peat swamp release site. What will you tell them? Do you have sufficient information to make an informed judgement on this question? Why or why not? b) An eager Indonesian master’s student arrives at your office the same week, and wishes to conduct a field study that could provide additional information upon which you might base such a decision in the future. What types of questions would you suggest that she investigates? Briefly consider study duration, study location, and the type of data to be collected. ...
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