Albores, J Biodivers Manage Forestry 2014, 3:1 http://dx.doi.org/10.4172/2327-4417.1000120
Journal of Biodiversity Management & Forestry
Research Article
Alpha, Beta and Gamma Diversity of the Birds in a Tropical Landscape of Southern Mexico Jorge E. Ramírez-Albores1,3*, José L. Rangel-Salazar1, Miguel A. Martínez-Morales2 and Jorge L. León1
Abstract Understanding the relationships between bird diversity and landscape structure in tropical forest fragments is paramount for the conservation of its biodiversity, particularly when tropical forest is under management. In this study, the alpha diversity variation of the bird community was evaluated, and its relationships with area, forest cover, environmental heterogeneity and altitude in a fragmented landscape of tropical forest in southern Mexico. A total of 243 bird species were recorded in the entire landscape. Alpha diversity spatially varies between sites from 123 to 158 species; WKLV YDULDWLRQ ZDV H[SODLQHG E\ KDELWDW KHWHURJHQHLW\ 2QO\ ¿YH vulnerable species increased their abundance with area, tropical forest cover and habitat heterogeneity increases. Beta diversity between sites ranged from 3% to 57%, and the average turnover between the study sites was 43%. Gamma diversity was largely determined by beta diversity than alpha diversity.
Keywords Avian communities; Landscape structure; Tropical forest; San Fernando; Central Depression of Chiapas
Introduction Landscapes are characterized by heterogeneity, consisting of a mosaic of environments that are perceived to various spatial and temporal scales. Spatial patterns of a species habitat may exert an important influence on its abundance and distribution, and consequently on population dynamics [1-3]. Habitat loss and changes in the spatial configuration and the synergies of these factors can alter the species diversity [4]. These changes can the lead the alteration of the amount and availability of resources, and conditions and ecosystem functioning [5,6]. The relationship between forest fragmentation and species diversity has often been studied using spatial models. A primary approach to explain this relationship is the island biogeography theory, which emphasizes the relationship between the size and degree of isolation of the fragments with species richness [7]. However, numerous studies suggest that significant changes in species richness occur in response to changes induced by human activities; particularly habitat loss and fragmentation of native vegetation cover [8-10]. Additionally, several studies have *Corresponding author: Jorge E. Ramírez-Albores, Instituto Potosino de ,QYHVWLJDFLyQ&LHQWt¿FD\7HFQROyJLFD$&&DPLQRDOD3UHVD6DQ-RVp &RO/RPDV6HFFLyQ6DQ/XLV3RWRVt6DQ/XLV3RWRVt&30p[LFR E-mail:
[email protected] Received: July 12, 2013 Accepted: January 29, 2014 Published: February 03, 2014
International Publisher of Science, Technology and Medicine
a SciTechnol journal been focused on understanding the effect of various mechanisms associated with fragmentation, especially the edge effect [11,12], and the interaction between the biota of fragments and the landscape, that consists of a mosaic of different vegetation types [13,14]. Landscape attributes can influence the composition and abundance of birds, and these can promote or interfere with the permanence of some species (e.g., endemic species), so this group has been considered useful indicators of biodiversity in the tropics because they respond rapidly to environmental changes, their biology is relatively well known and they are relatively easy to sample and to assess habitat quality [15-17]. Tropical forests in Mexico and Central America have undergone dramatic changes due to deforestation and fragmentation; it has been shown that these changes have precipitated changes in the bird diversity [18]. It has been also found that some bird communities may respond differently to changes in vegetation structure [17,19-21]. While these changes have been most evident in the distribution and abundance of particular taxa or specific habitat requirements [22-24], it is necessary to understand the way how groups with a wide distribution respond to changes in the structure and composition of the landscape. Understanding the relationships and the factors that determine the structure and composition of the bird community provides valuable information on the anthropogenic impact and alteration of the environment on species populations, that may be sensitive to changes in the landscape, which is important for management and to assess appropriate strategies for the conservation of the original forest patches and the species that inhabit them. In this sense, species bird richness and abundance can help us to understand the variation of local diversity (α, alpha diversity) and the complement of species composition among sites within the region (β, beta diversity), and how these diversities make regional diversity (γ, gamma diversity), and what is its relation to the variation in area, proportion of tropical forest cover, and different levels of environmental heterogeneity and altitude. In this study the variation of local diversity (α, alpha diversity) and species turnover (β, beta diversity) of the bird community in relation to the anthropogenic landscape structure of the Central Depression of Chiapas in Southern Mexico was evaluated.
Methods Study area The study was located in the municipality of San Fernando, Chiapas in the physiographic region known as Central Depression of Chiapas in Southern Mexico (16°52’18”N, 93°12’21”W, Figure 1), between 600 to 1100 m elevation and in an area of 258.3 km2. San Fernando is one of the most populous areas of Chiapas and has been dramatically transformed due to growing demand of land for anthropogenic use. The climate of the region varies from warm subtropical with summer rains (May to October, being May the hottest month) to semi-warm humid at altitudes above 1000 meters. The average annual temperature is 18 °C and total annual rainfall is 1200 mm [25]. Native vegetation is represented by tropical deciduous forest, and a mixture of other communities such as tropical semi-deciduous forest, oak forest and gallery forest. Modified environments include crops or agriculture fields (e.g., Zea mays, Phaseolus spp.), cattle pastures (or abandoned pastures),
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Citation: Ramírez-Albores JE, Rangel-Salazar JL, Martínez-Morales MA, León JL (2014) Alpha, Beta and Gamma Diversity of the Birds in a Tropical Landscape of Southern Mexico. J Biodivers Manage Forestry 3:1.
doi:http://dx.doi.org/10.4172/2327-4417.1000120
Figure 1: (a) Location of study sites in the landscape San Fernando, Chiapas, Mexico (Southern Mexico; Google Earth 11 June 2010), and (b) some images of the study sites (Photos by J.E. Ramírez-Albores).
Table 1: Local diversity birds and landscape attributes of study sites in San Fernando, Chiapas, Mexico. Habitats: Cp (cattle pastures and abandoned pastures), He KHGJHURZVRUOLYHIHQFHV *I JDOOHU\IRUHVW 6I VHFRQGDU\IRUHVW $I DJULFXOWXUDO¿HOGV 2I RDNIRUHVW 6X VXEXUEDQ]RQH Sites /RFDOGLYHUVLW\REVHUYHG ĮO)
1
2
3
4
5
6
7
8
9
10
11
12
13
151
126
123
158
150
145
125
135
151
126
130
137
146
/RFDOGLYHUVLW\HVWLPDWHG ĮE)
162
134
131
164
156
154
131
142
156
135
136
140
152
Local diversity observed DYHUDJHG ĮOA)
51.2
44.9
45.7
60.5
55.7
57.6
47.1
54.9
64.4
47.9
49.9
55.9
45.3
Area (ha)
83
120
24.6
31.8
22.5
44.7
55.5
34.3
31.7
56.3
29.9
38.3
47.1
Altitude ( m asl)
857
650
750
847
1003
852
895
1036
989
980
868
1077
1199
Tropical forest cover (%)
82
79
77
84
40
44
44
45
12
12
10
13
80
Habitat heterogenity (H’)
1.45
1.02
0.93
1.15
1.78
1.64
1.20
1.35
1.25
0.95
1.08
0.96
1.45
Habitats types
Gf, Sf, Af
Gf, Sf, Cp, Af, He
Sf, Cp
Gf, Sf, Cp, Af, He, Of
Sf, Cp, Af, He, Su
Gf, Sf, Cp, Af, He, Su
Sf, Cp, Af, He
Gf, Sf, Cp, Af, He
Sf, Cp, Af, He
Sf, Cp, Af, He
Sf, Cp, Af, He
Sf, Cp, Af, He
Gf, Sf, Af, He
secondary forest, hedgerows (or live fences), abandoned pastures and suburban areas (Figure 1). The most common native trees within the study area are Pistacia mexicana, Cochlospermum vitifolium, Ceiba spp., Bursera bippinata, B. simaruba, Zuelania guidonia, Gyrocarpus spp., Acacia cornigera, A. pennatula, Haematoxylum spp., Lysiloma spp., Alvaradoa amorphoides, Swietenia humilis, Ficus spp., Fraxinus purpusii, Sideroxylon celastrinum and Heliocarpus reticulatus [26].
Study sites The study sites were identified inspecting digital aerial images [27] and the area was examined on foot for confirmation of site suitability. Thirteen sites were chosen to represent the change in the landscape of San Fernando (Figure 1), these contained fragments of 9ROXPH,VVXH
tropical forest (e.g., tropical deciduous and semideciduous forest), and it’s usually were inside a matrix of agricultural fields and/or cattle pastures (or abandoned pastures), associated with other habitats such as gallery forest, secondary forest, hedgerows and oak forests. The proportion of tropical forest in each site varies from 10 to 84% (Table 1) [27]. ArcView GIS® 3.1 was used to estimate the area occupied by different habitats in each site (Table 1). With these estimates, habitat heterogeneity expressed by the Shannon diversity index (H’) was derived from the proportion of each habitat at each site [1,28].
Bird sampling Monthly visits were made to each site from February 2003 to January 2004. Point counts were used to assess species richness and xPage 2 of 8 x
Citation: Ramírez-Albores JE, Rangel-Salazar JL, Martínez-Morales MA, León JL (2014) Alpha, Beta and Gamma Diversity of the Birds in a Tropical Landscape of Southern Mexico. J Biodivers Manage Forestry 3:1.
doi:http://dx.doi.org/10.4172/2327-4417.1000120 abundance in each study sites. The method of single-and doubleobserver point counts was employed complementary fixed radius of 25 m [29,30]. Census points were surveyed for 10 min and there was a travelling distance of about 5 min (approximately 100 m) between points, to assure independence between neighboring points [29,30]. In total, 1560 census points sampled in the study area at the end of fieldwork. The census period ran for 4 h after dawn and for 3 h before dusk. At each census point, all bird species detected visually or acoustically were recorded, and whenever possible, detection distance from the observer was measured with an optical rangefinder. Vulnerable bird species were classified according to its endemic (e.g., endemic and quasi-endemic) [31] to Mexico and endangered status sensu SEMARNAT [32]. The abundances of these species were adjusted to a common scale, since sampling effort varied among sites. Thus, the relative abundance of species refers to the mean number of individuals recorded per study site. Bird species were categorized into 14 broad feeding guilds categories: carnivore (species consuming mainly live or dead vertebrates), insectivore (foliage, understory, canopy, ground, bark, and aerial insectivore), frugivore, nectarivore, granivore, omnivore and aquatic feeders (consuming fish, arthropods or vegetation, but mainly in aquatic environments) based upon primary components of the diet or subdiet obtained directly from field information and with supplemental information from literature [20,33].
Data analysis Local diversity (α, alpha diversity) was considered the cumulative species richness or the total number of bird species recorded (local diversity observed, αO) for each of the sites [34], and also was considered the average monthly species richness of each site (local diversity averaged, αOA). Three species accumulation functions
(Chao1, Chao2 and ICE) [35,36], which are asymptotic models, were used to fit the species accumulations: the linear dependence model and the Clench model. Smoothed accumulation curves was obtained through repeated random reordening (50 repetitions) of the samples in EstimateS 9.1 program [35,36]. An alternate representation of local diversity (α) is the estimated species richness obtained with the process of accumulation of species (local diversity estimated, αE) [36]. Beta diversity (β) between sites was calculated for each pairwise site comparison using the Sørenson index [37], in order to determine the degree of differentiation of diversity among sites. Regional diversity (γ, gamma diversity) was expressed as the cumulative number of bird species recorded in all sites of the studied landscape.
Relationship diversity-landscape To determine the relationship between local diversity of birds and landscape attributes of each site (area, tropical forest cover, habitat heterogeneity and altitude), we used a multiple regression model using the program STATISTICA ® 10. So prior distribution normalized variables to adjust the parametric assumptions of normality and homogeneity of variance, and where necessary, logarithmic transformations or arcsine were used [38]. A test of least squares multiple regressions to identify those covariates that explain the variation in observed (αO) and estimated (αE) was also carried out. Finally, generalized linear model (GLM) was used to determine the interaction of variables and distinguish the proportion of variance explained by each variable. Mantel tests were used to identify if landscape attributes were related to beta diversity (β) between sites [39]. Mantel routines estimate the association between two independent dissimilarity matrices that describe the same set of entities, and then test whether the association is stronger than
Figure 2: Species accumulation curves for birds at the 13 study sites and entire landscape in San Fernando, Chiapas (Southern Mexico). /RFDOGLYHUVLW\REVHUYHG ĮO DE DQGORFDOGLYHUVLW\HVWLPDWHG ĮE; c, d).
9ROXPH,VVXH
xPage 3 of 8 x
Citation: Ramírez-Albores JE, Rangel-Salazar JL, Martínez-Morales MA, León JL (2014) Alpha, Beta and Gamma Diversity of the Birds in a Tropical Landscape of Southern Mexico. J Biodivers Manage Forestry 3:1.
doi:http://dx.doi.org/10.4172/2327-4417.1000120 expected by chance [40]. The association between beta diversity and the five dissimilarity matrices (differences in area, tropical forest cover, habitat heterogeneity and altitude and distance between sites) was tested for all possible pairs of the thirteen sites. There were 500 permutations were used to test for significance at P=0.05. Feeding guild composition (proportion of species among guilds) was compared between study sites by performing G-tests. Finally, the abundance of species by feeding guilds was correlated with the ordination resulting from the non-metric multidimensional scaling (MDS). To compare the abundance of vulnerable species a t-test (P ≤ 0.05) was carried out, and a Kolmogorov-Smirnov [39] was also developed to identify which landscape attributes (area, tropical forest cover, habitat heterogeneity and altitude) relate to the abundance of this species between sites, as these are the most sensitive to changes in land use.
Results Regional diversity was represented by a total of 243 species of birds. The species accumulation curve showed that during the first four months of recording data 83% (185 species) of all species were observed (Figure 2). The Clench Model and non-parametric methods for estimating species richness indicated that the completeness of inventory for each site was above 97%, while for the entire landscape, it was above 95% (Figure 2). Sampling effort was adequate to represent the structure of bird assemblages at the study sites; rarefaction curves showed a similar pattern of accumulation and tend to reach an asymptote in all sites (Figure 2). As for the bird species richness at each site, local diversity (αO) represented, on average, 95% of estimated local diversity (αE), suggesting that inventories per site were relatively complete and so both richness comparable (χ2 = 39.3, df 11, P
