Pomacentrid Fishes near Bimini, Bahamas. R. D. Clarke ... er than to a large degree of habitat specialization. ...... Los Angeles Cty 14, 93-97 (1972). Heyer, W.R. ...
MARINE BIOLOGY
Marine Biology 40, 277-289 (1977)
9 by
Springer-Verlag 1977
Habitat Distribution and Species Diversity of Chaetodontid and Pomacentrid Fishes near Bimini, Bahamas R. D. Clarke Biology Department, Sarah Lawrence College; Bronxville, New York, USA
Abstract
The r e l a t i v e a b u n d a n c e of c h a e t o d o n t i d and p o m a c e n t r i d fishes in 8 h a b i t a t s , ranging in d e p t h f r o m 0.5 to 17 m, was d e t e r m i n e d by v i s u a l c o u n t i n g of f r e e - s w i m m i n g fish in the field. H a b i t a t w i d t h s and o v e r l a p s w e r e d e t e r m i n e d u s i n g w e i g h t i n g factors, d e v e l o p e d by C o l w e l l and F u t u y m a (1971), w h i c h a c c o u n t for the d i f f e r e n t d e g r e e of u n i q u e n e s s of each habitat. T h e a v e r a g e h a b i t a t w i d t h s and the a v e r a g e h a b i t a t o v e r l a p s w e r e g r e a t e r for the c h a e t o d o n t i d s than the p o m a c e n t r i d s . This was due, in part, to the g r e a t e r use of h a b i t a t s t r u c t u r e by the p o m a c e n t r i d s , and it is h y p o t h e s i z e d that this is b e c a u s e they are the m o r e v u l n e r a b l e to p r e d a t i o n . The j u v e n i l e s and a d u l t s r e a c h e d p e a k a b u n d a n c e in d i f f e r e n t h a b i t a t s for at least some of the species, and this m a y f u r t h e r r e d u c e the h a b i t a t - o v e r l a p v a l u e s for a d u l t s of some p a i r s of species. It is clear, however, t h a t the a b i l i t y of the s p e c i e s in t h e s e f a m i l i e s to c o e x i s t is l a r g e l y due to f a c t o r s o p e r a t i n g w i t h i n h a b i t a t s r a t h er than to a large d e g r e e of h a b i t a t s p e c i a l i z a t i o n .
Introduction
The g e n e r a l n o r t h - s o u t h i n c r e a s e in spec i e s d i v e r s i t y of m o s t taxa e x i s t s in the o c e a n s as w e l l as on land, w i t h the p o s s i b l e e x c e p t i o n of the d e e p s l o p e and a b y s s a l zones (Sanders, 1968). As tropical r a i n - f o r e s t s are c l e a r l y the m o s t d i v e r s e t e r r e s t r i a l c o m m u n i t i e s , so c o r a l reefs are the m o s t d i v e r s e m a r i n e c o m m u n i t i e s . Since the p r i n c i p l e of c o m p e t i t i v e e x c l u s i o n states that p o t e n t i a l l y c o m p e t i n g s p e c i e s can c o e x i s t at e q u i l i b r i u m o n l y by u t i l i z i n g d i f f e r e n t l i m i t i n g r e s o u r c e s (Miller, 1967), how do such d i v e r s e c o m m u n i t i e s p e r s i s t ? Resource types that vary continuously, such as food p a r t i c l e size, can p o t e n t i a l l y be b r o k e n d o w n into an i n f i n i t e n u m b e r of size c l a s s e s e a c h of w h i c h can be c o n s i d e r e d a s e p a r a t e r e s o u r c e . Bec a u s e it t a k e s a f i n i t e a m o u n t of a resource to s u s t a i n a p o p u l a t i o n , t h e r e is a f i x e d m a x i m u m n u m b e r of s p e c i e s a res o u r c e type c a n sustain, the n u m b e r dep e n d i n g on the total d e n s i t y , the res o u r c e range, the v a r i a b i l i t y and pred i c t a b i l i t y of e a c h p a r t of the range, and o t h e r factors. T h e s e f a c t o r s are und o u b t e d l y i n v o l v e d in the e x p l a n a t i o n of high s p e c i e s d i v e r s i t y on t r o p i c a l reefs,
but a n o t h e r f a c t o r m a y p l a y a role as well. A region may support more species t h a n w o u l d be p r e d i c t e d f r o m the a v a i l able r e s o u r c e s if p o t e n t i a l c o m p e t i tors o c c u p y d i f f e r e n t p a t c h e s , t h e r e b y a v o i d i n g d i r e c t c o n t a c t w i t h each other. P a t c h y d i s t r i b u t i o n s a p p a r e n t l y unrel a t e d to p h y s i c a l or b i o l o g i c a l factors are found in some t r o p i c a l taxa (Diamond, 1973), but m o r e o f t e n the p a t c h i n e s s is m a n i f e s t e d as h a b i t a t s p e c i a l i z a t i o n . In t h e s e cases, the s p e c i e s d i v e r s i t y of each h a b i t a t is less than the d i v e r s i t y for the r e g i o n (Whittaker, 1972). G r e a t e r b e t w e e n - h a b i t a t d i v e r s i t y in r e g i o n s w i t h m o r e s p e c i e s has b e e n d e m o n s t r a t e d in b i r d s (MacArthur et al., 1966), l i z a r d s (Pianka, 1969, 1971) , and d e c a p o d crust a c e a n s (Abele, 1974), b u t H e y e r and B e r v e n (1973) c o n c l u d e d that the g r e a t e r d i v e r s i t y of the t e r r e s t r i a l h e r p e t o f a u n a in E c u a d o r as c o m p a r e d to T h a i l a n d is l a r g e l y due to g r e a t e r w i t h i n - h a b i t a t d i v e r s i t y . In C o s t a Rica, O r i a n s (1969) found t h a t g r e a t e r bird d i v e r s i t y in w e t f o r e s t s c o m p a r e d to dry f o r e s t s was due in p a r t to g r e a t e r b e t w e e n - h a b i t a t div e r s i t y . Karr and R o t h (1971) f o u n d that h a b i t a t s e l e c t i o n in birds is m o r e precise in m a t u r e t r o p i c a l h a b i t a t s than in
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R.D. Clarke: Chaetodontid and Pomacentrid Habitat and Species Diversity
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