Community structure of invertebrate fauna in Central Chilean Rivers

River systems of Central Chile are short, steep and fast flowing. They are characterized by discharge regimes dominated by rainfall and snowmelt. Invertebrate fauna is highly endemic. This study aimed to describe the community structure of invertebrate in eight river systems in Central Chile (33-39°S) using species co-occurrence and niche sharing null models.

Methods

Invertebrate samples were collected from Central Chilean rivers (33-39°S), data were analyzed co-occurrence species and niche sharing null models for determine potential structuring patterns.

Results

The results revealed the presence of non-structured patterns in co-occurrence considering each site as well as all sites, that is most probably an effect of presence of many repeated species in the studied sites. Furthermore, we found the existence of niche overlap due to interspecific competition at each site and among all sites. The results obtained from these river systems corroborate observations from Chilean Patagonian Rivers.

Conclusion

This study contributes to understanding of biogeographical and ecological patterns of invertebrate communities in central Chilean Rivers and provide foundations for more complex ecological studies.

Keywords:
fluvial ecosystems; zooplankton; aquatic insects; crustaceans; null models

Site	Latitude	Longitude	Site	Latitude	Longitude	Site	Latitude	Longitude
Aconcagua 1	32°54’05.00”S	70°14’41.78”W	Mataquito 1	35° 02’57.90”S	70°31’44.46”W	Biobio 15	37°29’43.51”S	72°38’57.01”W
Aconcagua 2	32°54’57.63”S	70°19’38.14”W	Mataquito 2	34°58’03.67”S	71° 07’37.63”W	Biobio 17	37°39’03.79”S	71°44’07.37”W
Aconcagua 3	32°49’55.82”S	70°34’52.28”W	Mataquito 3	35°15’35.25”S	71° 02’37.28”W	Biobio 18	38° 02’14.07”S	71°47’27.81”W
Aconcagua 4	32°57’15.41”S	70°31’54.78”W	Mataquito 4	35°11’04.18”S	71° 06’58.08”W	Biobio 19	38° 03’09.99”S	71°43’23.60”W
Aconcagua 5	32°30’27.43”S	70°35’19.98”W	Mataquito 5	35° 07’25.69”S	70°58’03.36”W	Biobio 20	37°30’33.51”S	71°45’19.06”W
Aconcagua 6	32°46’34.91”S	71°12’43.47”W	Mataquito 6	35° 00’17.38”S	71°15’02.27”W	Biobio 21	37°33’02.63”S	72°17’05.06”W
Maipo 1	33°40’04.28”S	70°21’3.10”W	Mataquito 7	35° 03’42.28”S	71° 00’30.68”W	Biobio 22	37°20’32.70”S	71°48’00.30”W
Maipo 3	33°34’56.91”S	70°27’07.85”W	Mataquito 8	35°16’28.04”S	71° 00’51.52”W	Biobio 23	37°22’24.18”S	71°44’23.48”W
Maipo 4	33°20’57.83”S	70°21’54.21”W	Mataquito 10	34°54’26.47”S	71° 08’42.82”W	Biobio 24	37°19’04.02”S	71°41’08.51”W
Rapel 1	34°48’10.89”S	71° 02’03.88”W	Itata 1	36°34’04.62”S	71°13’25.94”W	Biobio 25	37°19’18.78”S	71°57’54.56”W
Rapel 2	34°44’41.96”S	70°46’55.14”W	Itata 2	36°40’22.87”S	71°17’01.00”W	Imperial 1	38°27’37.80”S	71°42’30.50”W
Rapel 3	34°27’26.25”S	70°59’22.08”W	Itata 3	36°39’53.88”S	71°19’01.29”W	Imperial 2	38°31’16.84”S	71°50’17.03”W
Rapel 4	34°16’35.93”S	71°21’53.89”W	Itata 4	36°37’23.12”S	71°26’18.90”W	Imperial 3	38°28’18.53”S	71°31’31.91”W
Rapel 5	34°21’07.85”S	70°21’39.30”W	Itata 5	36°31’21.10”S	71°35’55.83”W	Imperial 4	38°25’48.47”S	72° 00’21.84”W
Rapel 6	34°15’18.84”S	70°20’07.66”W	Itata 6	37° 08’24.32”S	71°40’15.20”W	Imperial 5	38°27’40.43”S	72°18’44.15”W
Rapel 7	34°12’17.95”S	70°31’4.04”W	Itata 7	37° 06’02.69”S	72° 07’49.27”W	Imperial 6	38°49’13.26”S	72°48’55.84”W
Rapel 9	34°14’06.89”S	70°32’45.19”W	Itata 8	37°12’49.01”S	72°26’04.71”W	Imperial 7	38°45’37.64”S	72° 04’47.26”W
Rapel 10	34°55’30.35”S	70°29’45.16”W	Itata 9	36°53’31.50”S	72°15’44.55”W	Imperial 8	38°36’26.20”S	71°55’41.58”W
Maule 1	35°37’35.94”S	71°18’00.54”W	Biobio 1	38°28’23.60”S	71°14’10.14”W	Imperial 9	38°52’05.40”S	72° 07’26.14”W
Maule 3	36°18’08.94”S	71°23’06.35”W	Biobio 2	38°12’40.03”S	71°17’47.86”W
Maule 4	36°22’38.08”S	71°36’54.14”W	Biobio 3	37°59’56.18”S	71°30’55.16”W
Maule 5	35°24’58.39”S	71° 02’27.69”W	Biobio 5	37°49’02.76”S	71°40’37.51”W
Maule 6	35°13’50.47”S	71°11’26.65”W	Biobio 7	37°12’39.31”S	72°19’15.78”W
Maule 7	35°54’30.91”S	71° 00’44.05”W	Biobio 8	37°12’49.01”S	72°26’4.71”W
Maule 8	35°42’18.92”S	71° 06’1.33”W	Biobio 9	37°13’55.11”S	72°34’25.46”W
Maule 9	35°51’47.75”S	71° 07’19.47”W	Biobio 10	38° 09’37.90”S	71°56’43.91”W
Maule 10	35°33’41.27”S	71°13’47.40”W	Biobio 13	37°51’34.99”S	72°37’33.85”W
			Biobio 14	37°34’36.91”S	72°38’17.91”W

Taxa reported in 2016	Taxa reported in 2017
Turbellaria	Mollusca
Turbellaria indet.	Gastropoda indet.
Nematoda	Insecta
Nematora indet.	Ephemeroptera
Insecta	Baetidae indet.
Ephemeroptera	Leptolephidae indet.
Astehenops sp.	Diptera
Coryphorus sp.	Chironomidae indet.
Chaquihua sp.	Diptera indet.
Hagenulopsis sp.	Plecoptera
Ephemeroptera indet.	Notoneuridae indet.
Plecoptera	Trichoptera
Austronemura sp.	Trichoptera indet.
Coeloptera	Crustacea
Ptilodactylidae indet.	Branchiopoda
Elmidae indet.	Daphnia sp.
Coleoptera indet.	Copepoda
Diptera	B. gracilipes
Ceratopogonidae	Calanoid copepodites
Blepharicidae indet.	Ostracoda
Chironomidae indet.	Ostracoda indet.
Ephidridae indet.	Amphipoda
Diptera indet	Hyalella sp.
Acari
Acari indet.
Crustacea
Branchiopoda
Daphnia ambigua Scourfield, 1947
Chydorus sphaericus O.F. Müller 1776
Copepoda
Boeckella gracilipes Daday, 1902.
Cyclopoid copepodites
Ostracoda
Ostracoda indet.

	Temperature	pH	Conductivity	Turbidity
Species richness
2016	-0.0007 (P = 0.980)	-0.2478 (P = 0.120)	-0.0003 (P = 0.595)	-0.1000 (P = 0.007) ^* * Significant associations (P < 0.05);
2017	-0.0756 (P = 0.111)	0.3561 (P = 0.378)	0.0004 (P = 0.658)	-0.0073 (P = 0.164)
Total individuals
2016	-0.1539 (P = 0.272)	-0.6619 (P = 0.382)	0.0068 (P = 0.023)*	-0.4010 (P = 0.024)*
2017	-0.2236 (P = 0.264)	0.3297 (P = 0.848)	0.0005 (P = 0.911)	-0.0211 (P = 0.348)

Species co-occurrence
	Mean index	Observed index	Variance	P
Total	16.79	16.78	0.05	0.49
Aconcagua	2.00	1.43	0.05	0.14
Maipo	2.00	1.43	0.05	0.14
Rapel	2.06	1.83	0.01	0.08
Maule	2.67	2.46	0.01	0.05
Mataquito	0.46	0.51	<0.01	0.99
Itata	3.60	3.54	0.04	0.36
Biobio	3.15	3.10	<0.01	0.32
Imperial	1.13	1.24	0.01	0.84
Niche sharing
	Mean index	Observed index	Variance	P
Total	0.55	0.38	< 0.01	<0.01 ^* * Significant associations (P < 0.05);
Aconcagua	0.55	0.38	< 0.01	<0.01*
Maipo	0.55	0.39	< 0.01	<0.01*
Rapel	0.55	0.38	< 0.01	<0.01*
Maule	0.55	0.39	< 0.01	<0.01*
Mataquito	0.55	0.38	< 0.01	<0.01*
Itata	0.55	0.38	< 0.01	<0.01*
Biobio	0.55	0.39	< 0.01	<0.01*
Imperial	0.55	0.39	< 0.01	<0.01*

Species co-occurrence
	Mean index	Observed index	Variance	P
Total	6.03	5.90	0.01	0.19
Rapel	0.83	0.83	0.00	0.99
Maule	1.33	1.06	0.01	0.20
Mataquito	1.33	1.06	0.01	0.20
Itata	1.61	1.57	<0.01	0.64
Biobio	2.90	2.87	<0.01	0.45
Niche sharing
	Mean index	Observed index	Variance	P
Total	0.55	0.39	<0.01	<0.01 ^* * Significant associations (P < 0.05);
Rape	0.55	0.39	<0.01	<0.01*
Maule	0.55	0.39	<0.01	<0.01*
Mataquito	0.55	0.39	<0.01	<0.01*
Itata	0.55	0.39	<0.01	<0.01*
Biobio	0.55	0.39	<0.01	<0.01*

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