Notes on the arthropod fauna of Salas y Gómez island, Chile

Abstract

Background: Salas y Gómez is a small, volcanic island largely untouched by humans due to its diminutive size and remoteness. Since the waters surrounding Salas y Gómez were established as Motu Motiro Hiva Marine Park in 2010, marine investigations have been the primary research focus. Secondarily, nesting seabird communities have been censused since 2011.
Methods and findings: In 2016, terrestrial arthropods were sampled on the island. Two observers sampled two locations for 30 min per site. Fifteen morphospecies were identified including at least one likely undescribed species.
Conclusions: Our work represents the most comprehensive terrestrial arthropod inventory of Salas y Gómez island to date. We are hopeful the recommendations provided will spur additional research to both characterize the island's arthropod community, as well as identify species of management concern.

Full text

S H O R T R E P O R T Open Access
Notes on the arthropod fauna of Salas y
Gómez island, Chile
Samantha N. Hershauer
1
, Sebastian Yancovic Pakarati
2
and J. Judson Wynne
1,3*
Abstract
Background: Salas y Gómez is a small, volcanic island largely untouched by humans due to its diminutive size and
remoteness. Since the waters surrounding Salas y Gómez were established as Motu Motiro Hiva Marine Park in
2010, marine investigations have been the primary research focus. Secondarily, nesting seabird communities have
been censused since 2011.
Methods and findings: In 2016, terrestrial arthropods were sampled on the island. Two observers sampled two
locations for 30min per site. Fifteen morphospecies were identified including at least one likely undescribed species.
Conclusions: Our work represents the most comprehensive terrestrial arthropod inventory of Salas y Gómez island to
date. We are hopeful the recommendations provided will spur additional research to both characterize the island’s
arthropod community, as well as identify species of management concern.
Keywords: Species inventory, Motu Motiro Hiva Marine park, Oceanic islands, Polynesia
Background
Prior to this study, our knowledge concerning the
natural history of Salas y Gómez island was largely
limited to the marine animals and pelagic bird rookeries.
The marine ecosystem is characterized by high biodiver-
sity including numerous endemic species [1,2]. More
than 38% of fish species found in Salas y Gómez waters
are considered endemic to the island [2]. While surveys
to initially document seabirds occurred earlier on [3–5],
annual pelagic bird surveys have been conducted since
2011 [6]. To date, at least at least 16 avian species nest
on the island [3–6].
Given the importance of the marine ecosystem, the
waters surrounding Salas y Gómez island were designated
as a “Natural Sanctuary”in 1976 [8]. In 2010, the Chilean
government established Motu Motiro Hiva Marine Park; at
which time 150,000 km
2
were designated a “no take zone”
[9] (i.e., fishing and other resource extraction activities
were prohibited [10]). In 2017, with support from the
Rapanui people, the Chilean government ultimately
declared the remaining 74% of the 579,368 km
2
aquatic
territory as protected [11]. Today, this region represents
the largest marine protected area in South American
waters [2] and one of the largest in the world.
Regarding our knowledge of terrestrial arthropods on
the island, only one species, Cryptamorpha desjardinsii
(Guérin-Méneville, 1844) (Coleoptera: Silvabidae) was
previously documented on the island [7]. In 2012,
arthropods were collected during the Ministry of Agricul-
ture’s National Forest Corporation’s (CONAF) annual bird
monitoring survey; researchers collected specimens belong-
ing to the orders Coleoptera, Lepidoptera, Diptera, and
Araneae [6]. Unfortunately, no additional information was
available on this survey.
In 2016, the second author (S.Y. Pakarati) and another
researcher collected terrestrial arthropods on Salas y
Gómez island during CONAF’s annual bird monitoring
survey. Here we present the findings of that work, which
represent the most comprehensive arthropod inventory
to date. Based upon our findings, we also provide recom-
mendations for future research and management.
© The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give
appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if
changes were made. The images or other third party material in this article are included in the article's Creative Commons
licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons
licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain
permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
* Correspondence: jut.wynne@nau.edu
1
Department of Biological Sciences, Colorado Plateau Museum of Arthropod
Biodiversity, Northern Arizona University (NAU), Flagstaff, USA
3
Center for Adaptable Western Landscapes, NAU, Flagstaff, USA
Full list of author information is available at the end of the article
Revista Chilena de
Historia Natural
Hershauer et al. Revista Chilena de Historia Natural (2020) 93:4
https://doi.org/10.1186/s40693-020-00093-w

Methods
Study area
Motu Motiro Hiva Marine Park (the marine park
surrounding Salas y Gómez island) is one of the most
remote and pristine protected areas of the South Pacific
[12]. Often considered the easternmost extent of the
Polynesian triangle (e.g., [13]), Salas y Gómez occurs
within the Chilean province of Easter Island and is
grouped with the surrounding small islands to form the
East Island Ecoregion (EIE) [14].
Salas y Gómez is a volcanic island, which rose ~ 3500 m
from the ocean floor around two million years ago [1,2].
Approximately 3300 km from mainland Chile, 402 km
northeast of Rapa Nui (Easter Island), and 2600 km from
the Juan Fernandez Islands, this small, isolated island is
uninhabited by humans [3]. Low, relatively flat, and
horseshoe-shaped, Salas y Gómez encompasses an area of
2.5 km
2
. Highest elevations occur at the eastern and west-
ern ends with the eastern extent reaching ~ 30 m above sea
level. The eastern and western extents of the island are
linked by a low-lying isthmus subjected to flooding during
storm events and a small sandy beach occurs along the
northeastern shore. Salas y Gómez supports relatively low
plant diversity consisting of three succulent species [5]and
shore spleenwort (Asplenium obliquum Forst) [5,15].
Arthropod Sampling & Analysis
On August 23, 2016, the second author (S.Y. Pakarati)
and Edgardo Quezada (Servicio Agricola y Ganadero
[SAG], Valparaíso Region, Rapa Nui Office) collected ar-
thropods. As the primary objective of this expedition
was the annual bird monitoring surveys conducted by
CONAF, search time was limited. Within each of the
two areas sampled (Fig. 1), two observers searched for
arthropods for approximately 30 min by examining vege-
tation, the soil, and underneath rocks (totaling 2 person
hours of searching).
Arthropods were hand-collected with forceps and
watercolor paintbrushes and then placed directly into vials
with 95% ethanol. Specimens were examined and photo-
graphed at the Colorado Plateau Museum of Arthropod
Biodiversity, Department of Biological Sciences, Northern
Arizona University. All specimens will ultimately be
deposited at the Museo Nacional de Historia Natural in
Santiago, Chile.
Results
Forty-six specimens across 15 morphospecies repre-
senting 10 taxonomic orders were collected (Table 1,
Figs. 2,3and 4). Lepidoptera represented the highest
species diversity (n= 3), while terrestrial isopods were
most abundant (nine individuals). Low-level taxonomic
identifications include a morphospecies of Segestriidae
(Araneae), Garypus sp. (Pseudoscorpiones: Garypidae),
Atheta sp. (Coleoptera: Staphylinidae), Entomobrya atro-
cincta Schott, 1896 (Entomobryomorpha: Entomobryidae),
Lynchia americana Leach, 1817 (Diptera: Hippoboscidae),
and a morphospecies of Trogiidae (Psocoptera). Total num-
ber of morphospecies per taxonomic group are summarized
(Fig. 2) and an annotated species list is provided (Table 1).
Discussion
While baseline in nature, this study represents the most
detailed arthropod study of Salas y Gómez. At least 15
Fig. 1 Salas y Gómez island, Chile with the two sampling locations demarcated (red dots)
Hershauer et al. Revista Chilena de Historia Natural (2020) 93:4 Page 2 of 6

morphospecies exist on this remote island. Of the 46 indi-
viduals collected, two morphospecies (E. atrocincta and L.
americana) were identified to species level (Fig. 4). Addition-
ally, the Segestriidae morphospecies (Fig. 3b) is being for-
mally described as a new species (D. Cotoras, pers. comm.
2018). It is likely to be the first endemic arthropod species
discovered on Salas y Gómez and may ultimately represent
the first terrestrial species of management concern.
For the remaining 12 morphospecies, there were vari-
ous obstacles in achieving higher taxonomic resolution.
For the pseudoscorpion, we collected one tritonymph of
the genus Garypus (Fig. 3a). While this also likely repre-
sents a new and endemic species (M. Harvey, pers. comm.,
2019), examination of adult characters is required to prop-
erly identify arachnids to species level. To both confirm
whether this is a new endemic species and to formally
describe it, we will require additional specimens (i.e.,
multiple adult males and females). The Staphylinid beetle,
Atheta sp. (Fig. 3d), cannot be identified beyond the genus
level because Chilean Aleocharinae are presently unidenti-
fiable. Original descriptions of congeners are insufficient
to reliably identify the specimen, and aside from a few
select genera, no one is actively working on this group (V.
Assing, pers. comm. 2019). Regarding the two terrestrial
isopod morphospecies (Halophilosciidae? sp. 1 and 2), we
suggest these two isopod morphospecies may belong to
the genus Littorophiloscia (S. Taiti, pers. com. 2020);
however, these specimens will require examination by an
isopod systematist to confirm.
As would be expected, avian species richness (i.e., total
number of species) increased as additional surveys (i.e.,
when more time was allocated) were conducted [4–6,12].
Schlatter [12] reported six species based upon brief site
visits by naturalists; unfortunately, no survey methods
were presented. Today, 16 seabird species are known from
the island [6]. The arthropod inventory results presented
here were similarly constrained by time. Because the pri-
mary objective of the 2016 work was to census seabirds,
observers spent only two person hours collecting arthro-
pods. Through this abbreviated effort, at least 15 morpho-
species were identified, which stands as a testament to the
significance of continuing this work. Importantly, we iden-
tified several research questions that should be addressed
to best guide future conservation and management efforts.
First, what options exist for expanding this inventory
work and/ or developing future arthropod monitoring
Table 1 Annotated species list of the 15 morphospecies from
Salas y Gómez island, Chile
Arachnida: Araneae
Araneae sp.
Segestriidae
Segestriidae sp.
Pseudoscorpiones
Garypidae
Garypus sp.
Insecta
Collembola
Entomobryidae
Entomobrya atrocincta Schott, 1896
Zygentoma
Zygentoma sp.
Hemiptera
Miridae sp.
Fulgoromorpha
Fulgoromorpha sp.
Psocoptera
Trogiidae
Trogiidae sp.
Coleoptera
Staphylinidae
Atheta sp.
Lepidoptera
Lepidoptera larva sp. 1
Lepidoptera larva sp. 2
Noctuidae
Noctuidae sp.
Diptera
Hippoboscidae
Lynchia americana Leach, 1817
Isopoda
Halophilosciidae? sp. 1
Halophilosciidae? sp. 2
Fig. 2 Total number of individuals collected across the 10
taxonomic groups detected on Salas y Gómez island, Chile
Hershauer et al. Revista Chilena de Historia Natural (2020) 93:4 Page 3 of 6

strategies for Salas y Gómez island? To best capture
diversity and identify potential management concern
species, a multi-day sampling frame, which employ
multiple techniques, is highly recommended. This could
be accomplished by focusing future efforts on examining
the different habitat types. Harrison and Jehl [4] identi-
fied at least five different topographic features on the
island (which may serve as a proxy for different
habitats); these include (1) the eastern half of the island,
which is relatively uniform and flat; (2) a sandy beach on
the northeastern extent of the island; (3) steep-sided
rocky cliffs to the south rising to ~ 10 m elevation; (4) a
sandy depression approximately 70 m in diameter in the
west-central section of the island; and, (5) the more
rocky western half of the island. We have identified a
sixth area, pelagic bird nesting areas, which could reveal
Fig. 3 aGarypus sp., bSegestriidae morphospecies, cTrogiidae morphospecies, and dAtheta sp. from Salas y Gómez island, Chile
Fig. 4 aLynchia americana Leach, 1817, and bEntomobrya atrocincta Schott, 1896 (♀), from Salas y Gómez island, Chile
Hershauer et al. Revista Chilena de Historia Natural (2020) 93:4 Page 4 of 6

unique taxa. Each of these sites likely supports different
species. Sampling techniques to consider include con-
ducting timed searches within 1 m
2
quadrats and surface
pitfall trapping similar to previous work on Rapa Nui
[16], which would maximize our ability to best capture
diversity, provide a robust sampling frame, and establish
a framework for future monitoring efforts. These sam-
pling locations could be marked and revisited should
monitoring be required. Alternatively, if an intensive ef-
fort cannot be supported in the near future, we recom-
mend CONAF Rapa Nui personnel continue sampling
arthropods during their annual pelagic bird censuses.
Sampling arthropods annually would require a diminu-
tive time investment for CONAF (i.e., an additional 1 to
2 h per visit to search for and collect arthropods).
Elements of the above mentioned sampling design could
be incorporated whereby researchers establish a system-
atic framework for sampling the different habitat types
during each visit. Both of these repeatable approaches
and the derived data may ultimately be modified to
monitor endemic and/or indicator species.
The prevalence of Cryptamorpha desjardinsii should
be further examined and potentially monitored by
CONAF and SAG. Native to “tropical Asia”[17], this
nonnative species is predaceous in its larval stage [18].
As virtually nothing is known concerning the entomo-
fauna of Salas y Gómez island, it is unknown whether
this species is competing with and/or predating upon
endemic arthropod populations.
Additionally, understanding the relationship between
pelagic birds and arthropods could both improve moni-
toring of avian populations, as well as shed additional
light on bird-arthropod phoresy in the South Pacific.
Pseudoscorpions have been widely documented using
birds for dispersal [19–21]. Because nothing is known
about pelagic bird phoresy in this part of the South
Pacific Ocean, it is possible Garypus sp. (a potentially
undescribed species) arrived to Salas y Gómez island via
this method. Currently, no pseudoscorpions have been
identified on Rapa Nui [22–24]. We suggest conducting
arthropod surveys (to search for pseudoscorpions) on
Motu Nui (a small islet off the southwestern coast) and
Rano Raraku crater, the two primary pelagic bird rooker-
ies of Rapa Nui. If present on both islands, this could
launch an exciting investigation into another ecological
connection between these two geographical regions.
This study represents the small first step toward char-
acterizing the arthropod community of Salas y Gómez.
Although Motu Motiro Hiva Marine Park is a protected
area, little is known regarding the natural history of the
terrestrial fauna –with the exception of avian species.
As it is infeasible to manage what is unknown, a future
management plan will benefit from a baseline under-
standing of the terrestrial flora and fauna on the island.
We hope this project will serve to inspire future workers
to expand upon our efforts and acquire the data necessary
to most effectively manage the island’s terrestrial ecosys-
tem. Through such an initiative, researchers will both
collect the information necessary to characterize the
natural history, as well as contribute to the protection of
sensitive natural resources on Salas y Gómez island.
Conclusion
Two person hours spent sampling two locations in south-
eastern Salas y Gómez resulted in the identification of at
least 15 morphospecies. Albeit brief, these surveys under-
score the potential for additional work to better
characterize the arthropod communities, as well as identify
potential management concern species. Importantly, we are
hopeful this project will engender future research on Salas
y Gómez island. Given the paucity of information on the
terrestrial communities of Salas y Gómez, additional
research will be required to: (1) examine the potential
ecological relationships between Salas y Gómez and other
neighboring islands; (2) characterize potential dispersal
mechanisms between Salas y Gómez and neighboring
islands; and, (3) acquire the data necessary to develop
effective policies to best manage terrestrial island habitats.
Abbreviations
CONAF: Ministry of Agriculture’s National Forest Corporation; EIE: East Island
Ecoregion
Acknowledgements
The second author (S.Y. Pakarati) would like to thank the following for
making this research possible: Edgardo Quezada V. from Servicio Agricola y
Ganadero (SAG), Oficina de Rapa Nui; Pedro Lazo Hucke with CONAF, Rapa
Nui; Violeta Producciones of Rapa Nui; the Chilean Navy and the AP 41
Aquiles crew; and Consejo Asesor de Monumentos Nacionales (CAMN) and
Secretaria Tecnica de Patrimonio (STP) in Rapa Nui. Aaron Smith and Chris
Wirth assisted the lead author with imaging arthropod specimens. Ryan
Lumen provided comments leading to the improvement of this paper. Lab
technician, Anna Ross, as well as systematists Volker Assing (Staphylinidae),
Darko Cotoras (Araneae), Mark Harvey (Pseudoscorpiones), Frans Jassens
(Collembola), Edward Mockford (Psocoptera), and Stefano Taiti (Isopoda)
assisted with arthropod identifications. Frank Howarth provided useful
discussions on Lepidoptera taxonomy. Justine Baca provided Fig. 2.
Authors’contributions
Specimen collection: SYP. Specimen processing and analysis: SNH, JJW.
Manuscript preparation: SNH, JJW, SYP. All authors read and approved the
final version of the manuscript.
Funding
None.
Availability of data and materials
Specimens will ultimately be deposited at the Museo Nacional de Historia
Natural, Santiago, Chile.
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors have no competing interests.
Hershauer et al. Revista Chilena de Historia Natural (2020) 93:4 Page 5 of 6

Author details
1
Department of Biological Sciences, Colorado Plateau Museum of Arthropod
Biodiversity, Northern Arizona University (NAU), Flagstaff, USA.
2
Consejo
Asesor de Monumentos Nacionales de Chile - Rapa Nui, Manu Project, Rapa
Nui, and Laboratorio de Socioecosistemas, Departamento de Ecología,
Universidad Autónoma de Madrid, Madrid, Spain.
3
Center for Adaptable
Western Landscapes, NAU, Flagstaff, USA.
Received: 6 January 2020 Accepted: 20 May 2020
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