Biodiversity Data Journal :
Research Article
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Corresponding author: Eduardo Ríos-Jara (eduardo.rios@academicos.udg.mx)
Academic editor: Dimitris Poursanidis
Received: 30 Sep 2020 | Accepted: 28 Oct 2020 | Published: 11 Dec 2020
© 2020 Eduardo Ríos-Jara, Cristian Galván-Villa, María del Carmen Esqueda-González, Manuel Ayón-Parente, Fabián Rodríguez Zaragoza, Dafne Bastida-Izaguirre, Adriana Reyes-Gómez
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ríos-Jara E, Galván-Villa CM, Esqueda-González MC, Ayón-Parente M, Rodríguez Zaragoza FA, Bastida-Izaguirre D, Reyes-Gómez A (2020) Species richness and biogeographical affinities of the marine molluscs from Bahía de Chamela, Mexico. Biodiversity Data Journal 8: e59191. https://doi.org/10.3897/BDJ.8.e59191
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For more than 10 years (2007-2018), the benthic macroinvertebrates of Bahía de Chamela (Mexican Pacific) were sampled at 31 sites (0-25 m depth). A total of 308 species of the five main classes of benthic molluscs were obtained (106 bivalves, 185 gastropods, 13 polyplacophorans, two scaphopods and two cephalopods). This is a significant increase in the number of species (246 new records) compared to the 62 species previously recorded more than 10 years ago. The distribution in the 31 localities of the bay is given for the first time for most of the species, together with information on its ecological rarity (incidence in the samples). Two families of bivalves (Veneridae and Mytilidae) and three families of gastropods (Calyptraeidae, Muricidae and Collumbellidae) comprised ~ 30% of all species. Ecological rarity was evident with 45 families (45.0%) with only one species and 178 species (57.8%) collected in one site and 67 (21.8%) in two sites. The molluscs of Bahía de Chamela represent 12.2% of all species recorded in the Mexican Pacific. Their biogeographic affinities are mostly related to the Tropical Eastern Pacific (TEP) including the oceanic islands and a few are restricted to the Tropical Mexican Pacific (TMP). Some have broader distributions to adjacent northern and southern temperate regions of the American Pacific, one to the western Atlantic, two pantropical (PAN) and two cosmopolitans (COS). The range distribution of each species was reviewed and updated, thus finding that seven species have extended their ranges of geographic distribution.
Mollusca, Bivalvia, Gastropoda, Polyplacophora, Scaphopoda, Cephalopoda, richness, range extension, new records, checklist, biogeography, Tropical Eastern Pacific, Mexican Pacific
Although molluscs are one of the best-known groups of marine invertebrates in the Mexican Pacific (e.g.
During recent years, inventories performed in Bahía de Chamela have improved our knowledge of major marine taxonomic groups, including the resident seabirds of the islands and islets (
Bahía de Chamela is included in the Marine Priority Region 26, which was established as a region of main concern by the National Commission for the Knowledge and Use of the Biodiversity of Mexico (CONABIO); it is also part of the National System of Marine Protected Areas. The area of the protected polygon of the bay covers 1981 ha and includes a series of islands and islets, with the most representative marine environments of the TMP (
Bahía de Chamela is located in the central part of the Mexican Tropical Pacific between Punta Rivas (
Location and geographic position of the sampling sites in Bahía de Chamela. The method used to obtain the samples and the depth of each site is also shown. TD = naturalist´s trawling dredge, SK = direct search during snorkelling, SD = direct search during SCUBA diving, SI = direct search in the intertidal.
Sampling sites | Location | Latitude / Longitude | Depth (m) | Sampling method |
1 | Off the sandy beach of Perula 1 |
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7 | TD |
2 | Off the sandy beach of Perula 2 |
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8 | TD |
3 | Off the sandy beach of Perula 3 |
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5 | TD |
4 | Villa Polinesia |
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7 | TD |
5 | Off San Pedro Island |
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7 | TD |
6 | Channel between Cocinas and Pajarera |
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8 | SD |
7 | Channel of San Pedro Island |
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9 | SD |
8 | El Novillo Islet |
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7 | SD |
9 | Embarcadero |
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3 | SD |
10 | Estero Pérula |
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0.5 | SI |
11 | Off Pajarera Island |
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5 | SD |
12 | Mamut Islet |
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12 | SD |
13 | Cocinas Island exposed coast 2 |
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9 | SD |
14 | Cocinas Island protected coast 1 |
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6 | SD |
15 | Cocinas Island protected coast 2 |
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8 | SD |
16 | Cocinas Island protected coast 3 |
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12 | SD |
17 | Colorada Islet |
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8 | SD |
18 | Pajarera Island exposed coast 1 |
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15 | SD |
19 | Pajarera Island exposed coast 2 |
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25 | SD |
20 | Pajarera Island protected coast 1 |
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4 | SD |
21 | Pajarera Island protected coast 2 |
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8 | SD |
22 | Pajarera Island protected coast 3 |
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10 | SD |
23 | San Agustin Islet |
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5 | SD |
24 | San Andrés Islet |
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8 | SD |
25 | San Pedro Island exposed coast |
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10 | SD |
26 | La Negrita Islet |
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8 | SD |
27 | La Rosada |
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13 | SD |
28 | Los Anegados Islet |
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6 | SD |
29 | Los Negritos |
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1 | SI |
30 | Punta Chamela |
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2 | SI |
31 | Roca Perula |
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3 | SK, SD |
Collections were made from 31 sites in the bay between 2007 and 2018. Most localities were visited at different times during the warm-rainy and warm-dry seasons of the year for better coverage of the seasonality of the area. The intertidal and adjacent shallow subtidal (0.5–25 m depth) were considered in each site. However, since several small islands and inlets do not have a well-defined intertidal zone, in these sites, sampling was performed only in the subtidal. Sampling was performed through direct search both in the intertidal and in the shallow subtidal during snorkelling and SCUBA diving. In the intertidal zone, molluscs were recorded through a direct search on and beneath the rocks mainly during the low tides. Those found in sandy beaches were obtained by digging and then sieving the sand through meshes of 10 mm. In the shallow subtidal, the molluscs were observed and identified in situ during snorkelling and SCUBA diving. Additionally, a naturalist´s trawling dredge (mesh size = 2.5 cm, cod-end mesh size = 1.3 cm) (
Taxonomic identification was performed using specialized literature:
The sampling effort and the completeness of the species inventory were evaluated with sample-based rarefactions, using the number of species per sampling site (
The geographic distributions of each species were first reviewed in the specialized literature (e.g.
A total of 308 species of five classes of molluscs were found in Bahía de Chamela (Suppl. material
Summary of the number and percentages of species, genera, families and orders of the five classes of molluscs recorded in Bahía de Chamela. The percentages represent the proportion of the total value of the same taxa for all mollusc groups.
Taxon | Bivalvia | Gastropoda | Polyplacophora | Scaphopoda | Cephalopoda | Total |
Species | 106 (34.4%) | 185 (60.1%) | 13 (4.2%) | 2 (0.6%) | 2 (0.6%) | 308 |
Genera | 72 (34.8%) | 123 (59.4%) | 9 (4.3%) | 2 (1.0%) | 1 (0.5%) | 207 |
Families | 29 (29.0%) | 63 (63.0%) | 6 (6.0%) | 1 (1.0%) | 1 (1.0%) | 100 |
Orders | 14 (45.2%) | 14 (45.2%) | 1 (3.2%) | 1 (3.2%) | 1 (3.2%) | 31 |
As a result, the species accumulation curves, obtained from sample-based rarefactions, showed a tendency to the asymptote, indicating an acceptable representation of the species richness of Bahía de Chamela, according to the sampling effort performed during the present study. Thus, the non-parametric estimators showed completeness of 58.3% (Chao 2), 64.2% (Jackknife 1) and 53.0% (Jackknife 2) with a mean value of 58.1% suggesting an expected 540 species compared to the actual number recorded in the bay. Even so, the sample-based rarefaction curves suggest that our sampling effort was sufficient to do a good estimation of the theoretical total number of molluscs species from the bay (Fig.
Six sites of the bay registered the higher number of species: Pajarera Island protected coast 1 (50 spp.), Cocinas Island protected coast 2 (48), La Rosada (48) and Cocinas Island protected coast 1 (43), the channel of San Pedro (33) and off the sandy beach of Villa Polinesia (30). Three islets also recorded important numbers: San Andres (44), Mamut (37) and Colorada (34).
The curves of unique and duplicate species in Fig.
The ecological rarity of molluscs species in 31 sampling sites of Bahía de Chamela, México. The percentages refer to the proportion of unique and duplicated species to the total number of species of molluscs recorded.
Rarity | Bivalvia | Gastropoda | Polyplacophora | Scaphopoda | Cephalopoda | Total |
Unique | 45 (14.6%) | 129 (41.9%) | 1 (0.3%) | 1 (0.3%) | 1 (0.3%) | 179 (57.9%) |
Duplicate | 30 (9.7%) | 34 (11.0%) | 2 (0.6%) | 1 (0.3%) | 0 | 67 (21.8%) |
Although the 106 species of bivalves were recorded in most sites, 45 (14.6%) were considered as unique (with only one record) and 30 (9.7%) duplicate (recorded in two sites). Almost 25% (75 species) of bivalves contribute to the total rarity (unique + duplicates), therefore it is considered high. Three families included the highest number of species: Veneridae (21), Mytilidae (14) and Carditidae (9); but thirteen families (44.8%), only one species. Most genera (45, 62.5%) had only one species. The gastropods were recorded in all sites of the bay. Three families had the largest number of species Calyptraeidae (18), Columbellidae (19) and Muricidae (19), together representing 30.3% of the gastropods and 18.2% of all mollusc species. However, 30 families (48.4%) had only one species and 12 families (19.4%) two species. Gastropods included 129 (41.9%) unique and 34 (11%) duplicate species.
The revision of the biogeographic affinities shows that most of the species of molluscs of Bahía de Chamela are exclusive to the Realm TEP (299 species, 97.1%); these include many species with wider ranges of distribution towards the two adjacent realms: Temperate Northern Pacific (59 species, 19.2%) and Temperate South America (10, 3.2%). There are a few species also recorded in other tropical realms, such as the eastern and central Indo-Pacific and the American Atlantic, in addition to Temperate Southern Africa and even the Arctic Ocean. Finally, only two species are from PAN and two from COS (Table
Biogeographic affinities documented for the mollusc species of Bahía de Chamela, Mexico. The percentages refer to the proportion of species in a particular region to the total number of species recorded in the bay (308). * Five species, previously considered endemic to the Gulf of California, extend their distribution ranges south to Bahía de Chamela.
Biogeographic region | Number of species |
Realm Tropical Eastern Pacific (RTEP) | 299 (97.1%) |
Province Tropical East Pacific (TEP) | 296 (96.1%) |
Ecoregion Tropical Mexican Pacific (TMP) | 7 (2.3%) |
Tres Marias Islands, Mexico (ILTM) | 21 (6.8%) |
Ecoregion Revillagigedo Islands, Mexico (IREV) | 11 (3.6%) |
Ecoregion Clipperton Atoll (ICLI) | 2 (0.6%) |
Ecoregion Coco Island, Costa Rica (ICOC) | 18 (5.8%) |
Province Galapagos Islands, Ecuador (IGAL) | 43 (14.0%) |
Realm Temperate Northern Pacific (RTNP) | 59 (19.2%) |
Province Warm Temperate Northeast Pacific (WTNP) | 56 (18.2%) |
Ecoregion Corteziana (COR) | 28* (9.1%) |
Realm Temperate South America (RTSA) | 10 (3.2%) |
Province Warm Temperate Southeastern Pacific (WTSP) | 1 (0.3%) |
Realm Central Indo-Pacific (RCIP) | 1 (0.3%) |
Province Western Coral Triangle (WCT) | 1 (0.3%) |
Realm Eastern Indo-Pacific (REIP) | 1 (0.3%) |
Province Hawaii (HA) | 1 (0.3%) |
Realm Tropical Atlantic (RTA) | 6 (1.9%) |
Province Tropical Northwestern Atlantic (TNA) | 5 (1.6%) |
Province North Brazil Shelf (NBS) | 4 (1.3%) |
Province Tropical Southwestern Atlantic (TSA) | 2 (0.6%) |
Realm Temperate Southern Africa (RTSAF) | 1 (0.3%) |
Province Agulhas (AG) | 1 (0.3%) |
Realm Artic (RAR) | 1 (0.3%) |
Pantropical (PAN) | 2 (0.6%) |
Cosmopolite (COS) | 2 (0.6%) |
Seven species extend their geographic distribution ranges: two bivalves (Chione tumens and Caryocorbula ovulata) and five gastropods (Lottia stanfordiana, Tegula corteziana, Tegula verdispira, Anachis adelinae and Haminoea vesicula). The geographic distribution of these species has been documented as follows: Chione tumens: Pacific coast of BCS (250N) south to Cabo San Lucas, into the Gulf of California as far as north as Bahia La Choya and Babia San Carlos, Sonora (
The inventory of molluscs of Bahía de Chamela includes 12% of the 2,576 species registered in the Mexican Pacific and 6.7% of the 4,643 marine molluscs registered in Mexico (
When compared to other marine protected areas of the TEP, the richness of species of Bahía de Chamela is similar to Malpelo Island (393), Sanquianga (356) and Ensenada Utría (316) (
The 13 chiton species recorded in Bahía de Chamela are included in a single order (Chitonidae) and six families, this being good taxonomic representation for the bay since all intertidal and subtidal species (0-30 m depth) recorded in the TMP belong to the Order Chitonida and are contained in six families. The only genus, not recorded in the present study, was Lepidozona which, in the TMP, is represented by Lepidozona allynsmithi previously recorded in coral aggregations of Oaxaca (
The Scaphopoda had a relatively high ecological rarity due to the low number of species recorded in the bay; these have semi-infaunal life forms associated with sandy bottoms with a high level of organic matter where they aggregate. They were collected in sandy bottoms (4-10 m depth) offshore from Villa Polinesia sandy beach and San Andres Islet with a naturalist's trawling dredge. This restricted distribution to particular sites of the bay suggests a preference for habitats probably associated with greater amounts of organic matter and food (e.g. foraminifera). As Graptacme semistriata occurs both in the Caribbean and the Eastern Pacific, this may represent a case of sibling species (
Two species of cephalopods were recorded in Bahía de Chamela: Octopus hubbsorum and O. bimaculatus. Records of the Hubbs´s octopus O. hubbsorum at five sites indicate the species is well represented in the bay. This is the most common octopus in the Mexican Pacific with an ample distribution from the Gulf of California to Oaxaca. Only one individual of O. bimaculatus was found off the sandy beach of Perula during snorkelling at approximately 2 m depth. This is the first record of the species in the ay. Its geographic distribution includes the Northeast Pacific from California (Point Conception) south to Bahia Magdalena on the Pacific coast of the Baja California Peninsula and also from the head of the Gulf of California southwards along the continental coast of Mexico and Central America until Panama (
The increase in species reported for Bahía de Chamela is the result of the sampling carried out not only in the intertidal, but also in subtidal habitats with the implementation of different techniques over a long period (2007-2018). Frequently, the species richness of molluscs has been under-estimated due to inadequate coverage of the spatial heterogeneity, as a result of inappropriate sampling techniques, including the failure of the detailed review of soft sediments, macroalgae and even cracks and spaces under the rocks where many species are common. These limitations result in missing specialized species living in limited or specific areas or habitats. Indeed, previous studies on molluscs have pointed out the importance of considering these factors for more complete inventories (
Shallow-water marine mollusc faunas are distributed in a pattern of distinct, geographically-definable areas; their distribution differs strongly and predictably, based on their biogeographic affinities (i.e. species associated with cold, temperate or tropical zones) (
The bioregionalization of
In the RTEP, the species composition is likely to be determined by the presence of certain tropical ecosystems and oceanographic/topographic features. The dominant biogeographic forcing agents defining this realm may include isolation, upwelling, nutrient inputs, temperature regimes, currents and coastal complexity. Many studies have demonstrated that the boundaries of shallow-water faunal distribution are correlated to the boundaries of water masses (
Since the bay is close to the mouth of the Gulf of California, which is the northern boundary region of the RTEP, there are many species shared with the adjacent province Warm Temperate Northeast Pacific (WTNP). Included are some species previously considered endemic to the Gulf of California (i.e. Lottia stanfordiana, Tegula corteziana) and others that extend their range distribution from the west coast of the Baja California Peninsula and the Gulf of California (i.e. Chione tumens, Anachis adelinae, Haminoea vesicula).
Bahía de Chamela was established as a marine protected area in 2002 because it was recognized that it has a high biodiversity of flora and fauna (
The high biodiversity of the bay is also relevant for the conservation of the tropical Mexican Pacific ecosystems, given that over-exploitation of natural habitats and overfishing of some commercial species affect the biodiversity of this region. Conservation strategies must take into account rarity and community-level assessments, including species richness, habitat specificity, reproductive strategies and endemism (
The inventory of species presented here is merely an approximation to the real diversity of molluscs from the bay. Even so, the present work demonstrates that the marine fauna in Bahía de Chamela is well represented by most common families and orders of the five main classes of molluscs (bivalves, gastropods, polyplacophorans, scaphopods and cephalopods). The bay comprises one of the most important protected areas of the tropical Mexican Pacific; this is significant because it displayed high species richness and a large number of unique species. Since the bay is now a popular destination for tourists, efforts to preserve its ecosystems and species are essential. The methodological approaches to estimate the molluscs' diversity must be further improved and more considerable efforts are required in the search for less conspicuous species, those of small sizes, such as micro-molluscs and spec Accept special techniques for the search for very particular life forms, such as nudibranchs or stenotic species that are symbionts of other invertebrates and fish. The information about molluscs in Bahía de Chamela should be complemented with an analysis that includes an assessment of the α, γ and β diversity to determine their relative distribution on different spatial scales. Population studies are also required, in particular of the species of commercial interest, which contribute to an integral framework on the biology and ecology of these species which is essential for their conservation in the bay and throughout its range of distribution.
Special thanks to all the members of the field sampling team during the many years of this research; especially to Arizbeth Alonso and many enthusiastic students of biology from the Universidad de Guadalajara (UdeG). We want to thank Paul Valentich-Scott (Santa Barbara Museum of Natural History), Jerry Harasewych and Ellen Strong (National Museum of Natural History of the Smithsonian Institution at Washington, DC) for their kind help and the access to the mollusc collections during our visit to their home institutions to validate several species. The field station of the Instituto de Biología (Universidad Nacional Autónoma de México) offered important support in its facilities in Chamela.
Ríos-Jara and Galván-Villa initiated the work and investigated throughout the study period. Both authors participated in the initial writing of the manuscript, which was later reviewed and improved by all co-authors. At different times, during the 10 years of study, the co-authors Ayón-Parente, Esqueda-González, Rodríguez-Zaragoza and Bastida-Izaguirre carried out fieldwork, taxonomic identifications and updated the database. All the gastropods, bivalves and scaphopods were again reviewed by Ríos-Jara and Esqueda-González and the polyplacophorans by Reyes-Gómez.
Checklist of marine molluscs of Bahía Chamela with information on their local distribution in Bahia de Chamela, Mexico and the biogeographic affinities. Location and geographic position of the sampling sites in Table 1. Biogeographic classification based on the spatial units (Realms, Provinces, Ecoregions) proposed by Spalding et al. (2007).