My MPhil thesis

My MPhil thesis aims to investigate the subterranean ant genus Strumigenys, which is one of the most speciose ant genera in the world with 891 species currently described (Bolton, 2026). They are commonly encountered ants in leaf litter samples, often nesting under rocks, decaying logs and seeds. Their diversity peaks in Southeast Asia (Tang et al., 2023), however the full extent of the distribution is not fully understood, and there are still many species undiscovered to science which are at greater risk to anthropogenic impacts. Our lack of knowledge towards their species diversity (Linnean shortfall) and the extent of their biogeogrpahical distribution (Wallacean shortfall) impedes efforts to preserve native insect communities (Didham et al., 2020).

FIG. 1 - Brainstorm word cloud for my thesis.
FIG. 1 - Brainstorm word cloud for my thesis.

My thesis will be divided into 2 chapters: the first chapter will aim to revise the taxonomy of Strumigenys in Southeast Asia, and the second chapter will be focusing on building species distribution models of exotic Strumigenys species on a global scale.

Chapter 1

Numerous Strumigenys from Southeast Asia have already been described, mostly by European and American taxonomists (see Table 1), however due to their cryptic nature and lack of a robust sampling protocol very few species have been described per publication (see Fig. 2).

TABLE 1 - List of literature with descriptions of new Strumigenys species from Southeast Asia by year.
Author Year Journal Citation FullRef Sp_described
Bolton 2000 Memoirs of the American Entomological Institute Bolton, 2000 Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute 65:1-1028. 127
Brassard et al. 2020 ZooKeys Brassard et al., 2020 Brassard, F.; Leong, C.-M.; Chan, H.-H.; Guénard, B. 2020. A new subterranean species and an updated checklist of Strumigenys (Hymenoptera, Formicidae) from Macao SAR, China, with a key to species of the Greater Bay Area. ZooKeys 970:63–116. 1
Brown 1972 Entomologist’s Monthly Magazine Brown, 1972 Brown, S. C. S. 1972. Ponera punctatissima (Hymenoptera: Formicidae) in Dorset. Entomologist’s Monthly Magazine 108:61. 4
Brown 1948 Entomological News Brown, 1948 Brown, W. L., Jr. 1948b. Strumigenys karawajewi, new name for a Sumatran ant. Entomological News 59:44. 1
Brown 1949  Psyche (Cambridge) Brown, 1949 Brown, W. L., Jr. 1949d. A correction. Psyche (Cambridge) 56:69. 1
Brown 1949 Mushi Brown, 1949 Brown, W. L., Jr. 1949f. Revision of the ant tribe Dacetini. I. Fauna of Japan, China and Taiwan. Mushi 20:1-25 2
Brown 1953 American Midland Naturalist Brown, 1953 Brown, W. L., Jr. 1953g. Revisionary studies in the ant tribe Dacetini. American Midland Naturalist 50:1-137. 3
Brown 1954 Psyche (Cambridge) Brown, 1954 Brown, W. L., Jr. 1954. The Indo-Australian species of the ant genus Strumigenys Fr. Smith: S. chapmani new species. Psyche (Cambridge) 61:68-73. 1
Brown 1957 Quarterly Review of Biology Brown, 1957 Brown, W. L., Jr. 1957g. Centrifugal speciation. Quarterly Review of Biology 32:247-277. 1
Brown 1958 Mushi Brown, 1958 Brown, W. L., Jr. 1958d. A new Japanese species of the dacetine ant genus Epitritus. Mushi 31:69-72. 3
Brown 1959 Psyche (Cambridge) Brown, 1959 Brown, W. L., Jr. 1959. The Indo-Australian species of the ant genus Strumigenys Fr. Smith: group of S. godeffroyi in Borneo. Psyche (Cambridge) 65:81-89. 1
Brown 2000 Memoirs of the American Entomological Institute Brown, 2000 Brown, W. L., Jr. 2000b. [Untitled. Mitis-group. Pyramica mitis Brown sp. n.]. Pp. 441-443 in: Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute 65:1-1028. 1
Brown & Boisvert 1979 Psyche (Cambridge) Brown & Boisvert, 1979 Brown, W. L., Jr.; Boisvert, R. G. 1979 (“1978”). The dacetine ant genus Pentastruma (Hymenoptera: Formicidae). Psyche (Cambridge) 85:201-207. 1
Cameron 1886 Proceedings of the Manchester Literary and Philosophical Society Cameron, 1886 Cameron, P. 1886. On a new species of Strumigenys (S. lewisi) from Japan. Proceedings of the Manchester Literary and Philosophical Society 25:229-232. 1
De Andrade 1994 Stuttgarter Beiträge zur Naturkunde. Serie B (Geologie und Paläontologie) De Andrade, 1994 De Andrade, M. L. 1994b. [Untitled. Descriptions of new taxa: Rhopalothrix inopinata de Andrade n. sp.; Strumigenys nepalensis de Andrade n. sp.; Strumigenys assamensis de Andrade n. sp.]. Pp. 54-64 in: Baroni Urbani, C.; De Andrade, M. L. 1994. First description of fossil Dacetini ants with a critical analysis of the current classification of the tribe (Amber Collection Stuttgart: Hymenoptera, Formicidae. VI: Dacetini). Stuttgarter Beiträge zur Naturkunde. Serie B (Geologie und Paläontologie) 198:1-65. 2
Dong & Kim 2020 Asian Myrmecology Dong & Kim, 2020 Dong, M.; Kim, S.-K. 2020. A taxonomic study on the genus Strumigenys Smith, 1860 (Hymenoptera: Formicidae) from Korea with a description of new species. Asian Myrmecology 12:e012001:1-21. 10.20362/am.012001 1
Emery 1869 Annali dell’Accademia degli Aspiranti Naturalisti Emery, 1869 Emery, C. 1869b. Enumerazione dei formicidi che rinvengonsi nei contorni di Napoli con descrizioni di specie nuove o meno conosciute. Annali dell’Accademia degli Aspiranti Naturalisti. Secunda Era 2:1-26. 1
Emery 1887 Annali del Museo Civico di Storia Naturale Emery, 1887 Emery, C. 1887. Catalogo delle formiche esistenti nelle collezioni del Museo Civico di Genova. Parte terza. Formiche della regione Indo-Malese e dell’Australia (continuazione e fine). [concl.]. Annali del Museo Civico di Storia Naturale 25[=(2)5]:465-473. 1
Emery 1890 Bullettino della Società Entomologica Italiana Emery, 1890 Emery, C. 1890c. Studii sulle formiche della fauna neotropica. Bullettino della Società Entomologica Italiana 22:38-80. 3
Emery 1895 Annali del Museo Civico di Storia Naturale Emery, 1895 Emery, C. 1895m. Viaggio di Leonardo Fea in Birmania e regioni vicine. LXIII. Formiche di Birmania del Tenasserim e dei Monti Carin raccolte da L. Fea. Parte II. Annali del Museo Civico di Storia Naturale 34[=(2)14]:450-483 1
Emery 1897 Természetrajzi Füzetek Emery, 1897 Emery, C. 1897. Formicidarum species novae vel minus cognitae in collectione Musaei Nationalis Hungarici quas in Nova-Guinea, colonia germanica, collegit L. Biró. Természetrajzi Füzetek 20:571-599. 3
Forel 1905  Mitteilungen aus dem Naturhistorischen Museum in Hamburg Forel, 1905 Forel, A. 1905. Ameisen aus Java. Gesammelt von Prof. Karl Kraepelin 1904. Mitteilungen aus dem Naturhistorischen Museum in Hamburg 22:1-26. 5
Forel 1912 Entomologische Mitteilungen Forel, 1912 Forel, A. 1912a. H. Sauter’s Formosa-Ausbeute. Formicidae (Hym.) [Combined reference]. Entomologische Mitteilungen. Berlin-Dahlem 1:45-81. 1
General & Alpert 2025 Breviora General & Alpert, 2025 General, D. E. M.; Alpert, G. D. 2025. A remarkable new species of the ant genus Strumigenys F. Smith 1860 (Hymenoptera: Formicidae) from the eastern Philippines. Breviora 578 (1):1-8. [online early] 10.3099/0006-9698-578.1.1 1
Hamer et al. 2025 PLoS ONE Hamer et al., 2025 Hamer, M. T.; Katzke, J.; Tang, K. L.; Weemaels, A. I.; Hita-Garcia, F.; Economo, E. P.; Guénard, B. 2025. A revision of the rare Strumigenys mnemosyne (Formicidae; Myrmicinae) group using micro-CT scanning, with the description of three new species, and the virtual repair of a broken paratype. PLoS ONE 20 (9):e0331762, 1-29. 3
Ito 1914 Annales de la Société Entomologique de Belgique Ito, 1914 Ito, T. 1914a. Formicidarum japonicarum species novae vel minus cognitae. Annales de la Société Entomologique de Belgique 58:40-45. 1
Lin & Wu 1996 Chinese Journal of Entomology Lin & Wu, 1996 Lin, C.-C.; Wu, W.-J. 1996. Revision of the ant genus Strumigenys Fr. Smith (Hymenoptera: Formicidae) of Taiwan. Chinese Journal of Entomology 16:137-152. 3
Lin & Wu 2001 Formosan Entomologist Lin & Wu, 2001 Lin, C.-C.; Wu, W.-J. 2001. Three new species of Strumigenys Fr. Smith (Hymenoptera: Formicidae) with a key to Taiwanese species. Formosan Entomologist 21:159-170. 3
Lyu 2007 Journal of Asia-Pacific Entomology Lyu, 2007 Lyu, D. 2007. A new species of Strumigenys (Hymenoptera: Formicidae) from Korea. Journal of Asia-Pacific Entomology 10:117-120. 10.1016/S1226-8615(08)60341-6 1
Mayr 1866 Abteilung Mayr, 1866 Mayr, G. 1866a. Myrmecologische Beiträge. Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften in Wien. Mathematisch-Naturwissenschaftliche Classe. Abteilung I 53:484-517. 1
Menozzi 1939 Tijdschrift voor Entomologie Menozzi, 1939 Menozzi, C. 1939b. Qualche nuova formica di Sumatra. Tijdschrift voor Entomologie 82:175-181. 1
Ogata 1990 Esakia Special Issue Ogata, 1990 Ogata, K. 1990. A new species of the ant genus Epitritus Emery from Japan (Hymenoptera, Formicidae). Esakia Special Issue 1:197-199. 1
Ogata & Onoyama 1998 Entomological Science Ogata & Onoyama, 1998 Ogata, K.; Onoyama, K. 1998. A revision of the ant genus Smithistruma Brown of Japan, with descriptions of four new species (Hymenoptera: Formicidae). Entomological Science 1:277-287. 1
Roger 1862 Berliner Entomologische Zeitschrift Roger, 1862 Roger, J. 1862a. Einige neue exotische Ameisen-Gattungen und Arten. Berliner Entomologische Zeitschrift 6:233-254. 1
Smith 1865 Journal and Proceedings of the Linnean Society of London Smith, 1865 Smith, F. 1865. Descriptions of new species of hymenopterous insects from the islands of Sumatra, Sula, Gilolo, Salwatty, and New Guinea, collected by Mr. A. R. Wallace. Journal and Proceedings of the Linnean Society of London. Zoology 8:61-94. 1
Stärcke 1941 Tijdschrift voor Entomologie Stärcke, 1941 Stärcke, A. 1941. Hersenganglion van Strumigenys; koloniestichting van Polyrhachis bicolor. Tijdschrift voor Entomologie 84:ii-xv. 1
Tang & Guénard 2023 European Journal of Taxonomy Tang & Guénard, 2023 Tang, K. L.; Guénard, B. 2023. Further additions to the knowledge of Strumigenys (Formicidae: Myrmicinae) within South East Asia, with the descriptions of 20 new species. European Journal of Taxonomy 907:1-144. 10.5852/ejt.2023.907.2327 19
Tang et al. 2019 ZooKeys Tang et al., 2019 Tang, K. L.; Pierce, M. P.; Guénard, B. 2019. Review of the genus Strumigenys (Hymenoptera, Formicidae, Myrmicinae) in Hong Kong with the description of three new species and the addition of five native and four introduced species records. ZooKeys 831:1-48. 10.3897/zookeys.831.31515 3
Taylor 1968 Journal of the Australian Entomological Society Taylor, 1968 Taylor, R. W. 1968e. A new Malayan species of the ant genus Epitritus, and a related new genus from Singapore (Hymenoptera: Formicidae). Journal of the Australian Entomological Society 7:130-134. 1
Taylor & Brown 1978 Pilot Register of Zoology Taylor & Brown, 1978 Taylor, R. W.; Brown, W. L., Jr. 1978. Smithistruma kempfi species nov. Pilot Register of Zoology Card No. 35:1-2. 2
Terayama 2020 Japanese Journal of Systematic Entomology Terayama, 2020 Terayama, M. 2020. A new species of the ant genus Strumigenys Smith, 1860 (Hymenoptera: Formicidae) from Japan. Japanese Journal of Systematic Entomology 26 (2):223-225. 2
Terayama & Kubota 1989 Japanese Journal of Entomology Terayama & Kubota, 1989 Terayama, M.; Kubota, S. 1989. The ant tribe Dacetini (Hymenoptera, Formicidae) of Taiwan, with descriptions of three new species. Japanese Journal of Entomology 57:778-792. 2
Terayama et al. 1995 Proceedings of the Japanese Society of Systematic Zoology Terayama et al., 1995 Terayama, M.; Lin, C.-C.; Wu, W.-J. 1995. The ant genera Epitritus and Kyidris from Taiwan (Hymenoptera: Formicidae). Proceedings of the Japanese Society of Systematic Zoology 53:85-89. 4
Terayama et al. 1996 Japanese Journal of Entomology Terayama et al., 1996 Terayama, M.; Lin, C.-C.; Wu, W.-J. 1996. The Taiwanese species of the ant genus Smithistruma (Hymenoptera, Formicidae). Japanese Journal of Entomology 64:327-339. 1
Wang 2000 Memoirs of the American Entomological Institute Wang, 2000 Wang, M.-S. 2000a. [Untitled. Pyramica sinensis Wang sp. n.]. P. 390 in: Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute 65:1-1028. 1
Wheeler 1919 Bulletin of the Museum of Comparative Zoology Wheeler, 1919 Wheeler, W. M. 1919. The ants of Borneo. Bulletin of the Museum of Comparative Zoology 63:43-147. 2
Wheeler 1929 Bollettino del Laboratorio di Zoologia Generale e Agraria della Reale Scuola Superiore d’Agricoltura Wheeler, 1929 Wheeler, W. M. 1929h. Ants collected by Professor F. Silvestri in Formosa, the Malay Peninsula and the Philippines. Bollettino del Laboratorio di Zoologia Generale e Agraria della Reale Scuola Superiore d’Agricoltura. Portici 24:27-64. 1
Xu 2000 Entomotaxonomia Xu, 2000 Xu, Z.-H. 2000. A new species of the ant genus Epitritus Emery (Hymenoptera: Formicidae) from China. Entomotaxonomia 22:297-300. 3
Xu & Zhou 2004 Acta Zootaxonomica Sinica Xu & Zhou, 2004 Xu, Z.-H.; Zhou, X.-G. 2004. Systematic study on the ant genus Pyramica Roger (Hymenoptera, Formicidae) of China. Acta Zootaxonomica Sinica 29:440-450. 1
Yoshimura & Onoyama 2007 Memoirs of the American Entomological Institute Yoshimura & Onoyama, 2007 Yoshimura, M.; Onoyama, K. 2007. A new sibling species of the genus Strumigenys, with a redefinition of S. lewisi Cameron. Pp. 664-690 in: Snelling, R. R.; Fisher, B. L.; Ward, P. S. (eds.) 2007. Advances in ant systematics (Hymenoptera: Formicidae): homage to E.O. Wilson – 50 years of contributions. Memoirs of the American Entomological Institute 80:690 pp. 1
Zhou 2001 Guangxi Normal University Press Zhou, 2001 Zhou, S. 2001a. Ants of Guangxi. [In Chinese.]. Guilin, China: Guangxi Normal University Press, 255 pp. 1
Zhou 2011 Sociobiology Zhou, 2011 Zhou, S. 2011. A new species of the genus Pyramica (Hymenoptera: Formicidae) from Nankunshan National Forest Park of Guangdong, South of China. Sociobiology 57:419-424. 1
Zhou & Xu 2003 Acta Zootaxonomica Sinica Zhou & Xu, 2003 Zhou, S.-Y.; Xu, Z.-H. 2003. Taxonomic study on Chinese members of the ant genus Strumigenys F. Smith (Hymenoptera: Formicidae) from the mainland of China. Acta Zootaxonomica Sinica 28:737-740. 1 
# Load library
library(ggplot2)
library(ggrepel)
library(ggtext)

# Load literature reference dataset
spec_ref <- read.csv("./spec_ref.csv")

# Calculate cumulative sum of species described in publications according to year
ref2 <- spec_ref%>%
        arrange(Year, Sp_described) %>%
        mutate(Sp_cum = cumsum(Sp_described))

# Generate cumulative species described graph
ggplot(ref2, aes(x=Year, y=Sp_cum))+
  geom_line()+
  geom_point(shape=1, size = 3)+
  scale_x_continuous(n.breaks = 10)+
  geom_label_repel(aes
                   (label=ifelse(Sp_described>10, as.character(Citation),"")),
                   hjust=1,
                   vjust=1,
                   size = 4,
                   box.padding   = 1,
                   point.padding = 0.5,
                   direction = "x")+
  xlab("Publication Year")+
  ylab("Cumulative species richness")
FIG. 2 - Cumulative richness of Strumigenys species described in Southeast Asia.
FIG. 2 - Cumulative richness of Strumigenys species described in Southeast Asia.

Only 2 publications have described more than 10 species from Southeast Asia: Barry Bolton’s “The ant tribe Dacetini” in 2000, and Tang & Guénard’s “Further additions to the knowledge of Strumigenys (Formicidae: Myrmicinae) within South East Asia, with the descriptions of 20 new species” in 2023. Both publications and another by Hamer et al. (2025) have provided detailed descriptions on species groupings and their diagnostic characters along with describing species new to science. Still the authors have noted that some species require more materials to further examine and determine whether more species could be delimitated from described species. This demonstrates a need for a revision for the genus where issues with species complexes and groupings could be resolved as more updated data is available.

The hypothesis for this chapter is that specimens can be identified to species level through comparisons with described species using morphological traits. If the null hypothesis could not be rejected then that specimen would be a new species to science.

The primary data for this chapter will be the ant specimens themselves. Specimens will be derived from 2 sources:

  1. Newly collected material will be sampled across Southeast Asia. 36-60 20x20 metre plots are established in primary and secondary forests and monoculture plantations below 1000 metres above sea level in each site, where each plot is spaced 100-200 metres apart from one another; At each corner leaf litter are collected from 1x1 metre quadrats, which are then processed using Winkler extractors for 72 hours with one reshuffling after 48 hours. More material will be randomly collected by hand during expeditions.

  2. Existing specimens will be examined in local collections (HKBM and IBBL) and loaned from overseas museums and collections. At the moment specimens have been loaned from collections in China, Japan and the United States.

For each specimen I have recorded information on their taxonomy, depository and collection information which are all stored in an excel sheet. For specimens where I cannot identify to species level using pre-existing literature and dichotomous to I will assign a unique morphocode for that particular specimen (see example in Table 2):

TABLE 2 - Extract of Strumigenys specimen record dataset
Coll_code Spec_code Subfamily Genus Species Species_group Caste Quantity Medium Microhabitat Habitat Method DateBegin DateEnd DateRoman CollectedBy Latitude Longitude LatLonError Elevation LocalName Adm2 Adm1 Country BiogeographicRegion
MTH2704-01 ANTWEB1012354 Myrmicinae Strumigenys MCHC sp.5 mnemosyne-group worker 3 95%ethanol;dry-mounted sifted and extracted leaf litter Mature forest R-Winkler 2/12/2025 2/12/2025 2.xii.2025 MTHamer 17.90763 104.7811 ±20 372 Phou Hin Boun National Park NA Khammouane Laos Indomalaya

Through examining newly collected specimens and those in existing collections, not only is it possible to find undescribed species that were previously misdiagnosed by other researchers, but I can also uncover new locality records which can provide further insight into the extents of the distribution of Southeast Asian Strumigenys species. For example, a specimen recently collected in an urban park in Malaysia was revealed to be the rare Strumigenys nannosobek, which was only previously known from India and Bhutan; A nest of Strumigenys nathistorisoc was recently collected in an urban park in South Korea, which was only previously recorded in Hong Kong and some mainland Chinese provinces. Both cases represent immense range expansions for some rarely collected species, and would not be possible without extensive sampling and examination of multiple collections.

More data will be recorded in this chapter in the form of images. Specimens of potentially new species will be photographed using the imaging stereomicroscope in our lab to obtain full-face, lateral and dorsal views, and any other diagnostic feature of the species group (see Fig. 3). All images will be added into PowerPoints to construct a morphospecies database for easier comparison and identification.

FIG. 3 - Figure plate of holotype specimen of Strumigenys MCHC sp.5 (to be further edited for publications).
FIG. 3 - Figure plate of holotype specimen of Strumigenys MCHC sp.5 (to be further edited for publications).

Because the image files are all in TIF format, I have made a code to compress the size of multiple images at once using the “magick” package.

# Load library
library(magick)

# Define the paths (I've put "folder.name" as substitute but any working directories with images will work)
input_folder <- "folder.name"
output_folder <- "folder.name"

# List all image files in the input folder
image_files <- list.files(input_folder, pattern = "\\.(tif|tiff)$", full.names = TRUE)
print("Detected TIFF files:")
print(image_files)

# Read all images at once
images <- image_read(image_files)
print(class(images))
print(length(images))

# Check if image was read successfully
if (is.null(images) || length(images) == 0) {
  cat("Image not valid or not read correctly:", image_file, "/n")
  next
}

# Compress all images into 1000x1000 pixels
compressed_images <- images %>% 
  image_resize("1000x1000>")
print(class(compressed_images))
print(length(compressed_images))

# Save each compressed image to the output folder
for (i in 1:length(compressed_images)) 
  {original_name <- tools::file_path_sans_ext(basename(image_files[i]))
  cleaned_name <- gsub("_ch00", "", original_name)
  output_filename <- paste0(cleaned_name, "-resize.tif")
  output_path <- file.path(output_folder, output_filename)
  image_write(compressed_images[i], path = output_path, quality = 100)}

Images will be used to compare specimens from different regions and with reference to morphological descriptions in existing literature to determine whether it is a new species. I will also attempt to make assign those without species groupings into groups based on their morphological features. Updates to diagnostic characters to species groupings will be made if additional characters are observed.

Morphological measurements (in mm, rounded off to 2 significant figures) of potentially new species will also be recorded using traits that were used by other researchers in existing literature (see example in Table 3):

TABLE 3 - Extract of Strumigenys morphological measurements dataset.
coll_code spec_code genus species caste status head_length head_width mand_length scape_length eye_length pronotum_width meso_length petiole_length petiole_height dorsal_petiole_width postpetiole_length postpetiole_width gaster_length hind_femur_length cephal_index mand_index scape_index eye_index femur_index lateral_petiole_index dorsal_petiole_index
MTH2704-01 ANTWEB1012354 Strumigenys MCHC sp.5 worker type 0.36 0.41 0.1 0.18 0.01 0.19 0.4 0.17 0.09 0.11 0.11 0.14 0.46 0.22 116.06 27.04 44.42 2.67 52.43 54.34 82.66

I am currently considering incorporating phylogenetic analyses and geometric morphometric analyses to potentially validate species groupings and resolve species complexes (such as the issue of Strumigenys feae noted by Tang & Guénard (2023)) but still needs to be discussed with Benoit, especially when there is often a lack of ethanol material for rare species to collect phylogenetic data as those singleton specimens would be dry-mounted and genetic material would be severely degraded.

For the storage and management of data in this chapter:

  • Literature references will be databased in an excel sheet (not Zotero as most are either paper print publications without DOI or physical books (Bolton, 2000), see Table 1) which is currently saved on my personal OneDrive with a backup copy on my USB. This will then be exported as a RIS file and uploaded as supplementary material during publication;
  • All specimen records and morphological measurements are stored in excel files on my personal OneDrive, with backup copies saved onto my USB whenever I make updates. The dataset will also be uploaded to the central lab drive and online data repositories such as Datahub as supplementary material during publication;
  • Specimen images and morphospecies powerpoints are all saved on my USB due to their large file sizes. Images of newly described species will be uploaded to AntWeb (online repository for ant specimen images, especially of type specimens), though procedures for this still needs to be discussed with Benoit;
  • Newly collected specimens using the standardized sampling protocol are also saved in a central dataset in Google Drive managed by another PhD student Matt Hamer as part of his community ecology study;
  • R-code for generating accumulation of Strumigenys species described from Southeast Asia and batch photo compression will be uploaded to Github when the project has ended.

Chapter 2

Amongst the 891 Strumigenys species described, there are 24 species that have successfully established populations in non-native land through accidental introduction pathways such as transportation of potted plants, of which 5 can be found in Hong Kong. However the full extent of their distribution, why are they able to spread more widely than their congeners, as well as which factors govern their worldwide spread are currently unknown.

My second chapter aims to use species distribution modelling (SDM) to map the most updated distribution of these exotic species and see if I can predict which areas they are mostly likely recorded in but have not been found by scientists yet. I would also like to investigate which environmental factors can more successfully model the distribution of these subterranean ants.

At the moment I am still reviewing literature to determine which modelling method is most suitable to test my hypotheses. There was a publication by Fitzpatrick et al. (2013) evaluated the effectiveness of predicting the distribution of ant species in New England between two modelling techniques, which they suggested that MaxLike has a greater performace in predicting the probability of species occurence than the conventional MaxEnt (predicts habitat suitability for a species). Searches on connectedpapers linked this publication to several literature regarding ecological niche modelling and how to reduce biases in the model (see Fig. 4):

FIG. 4 - Map by connectedpapers about similar literature to Fitzpatrick et al. (2013).
FIG. 4 - Map by connectedpapers about similar literature to Fitzpatrick et al. (2013).

connectedpapers is helpful in that it helps to visualize the degree of similarity in the research in different publications so I can find papers with similar topics to the chosen paper. The only downside that I find is that I can only build maps based on one paper at a time. With Research Rabbit not only can I include multiple papers to generate a similarity map, but I can also easily see the citation-reference relationship between the publications however the similarity in the contents of the publication is not as clear. In this case I used Fitzpatrick et al. (2013) with 2 publications investigating how to reduce sampling biases when using MaxEnt modelling (Kramer-Schadt, 2013; Boria, 2014), both of which I derived from my results in connectedpapers (see Fig. 5):

FIG. 5 - Map by Research Rabbit about similar literature to Fitzpatrick et al. (2013), Kramer-Schadt (2013) and Boria (2014).
FIG. 5 - Map by Research Rabbit about similar literature to Fitzpatrick et al. (2013), Kramer-Schadt (2013) and Boria (2014).

All relevant papers that I have obtained from both search engines and on Google Scholar will be saved into my SDM literature collection in Zotero.

One direction I have considered is to compare between exotic Strumigenys species with native common Strumigenys species using SDMs and to investigate why these 24 species are more successful at spreading worldwide than some common species. I was wondering if I could model their ecological niche to make interspecific comparisons.

I have also found recent studies from Korea highlighting the importance of the selection of explanatory variables to be included in SDMs for ants (Jung et al., 2021; Kwon et al., 2024). In the latter study they demonstrated how SDMs using soil microclimatic variables hold a greater predictive power than those using macroclimatic variables when modelling the distribution of invasive ant species. While both studies were conducted in temperate regions, they provide intriguing thoughts into how we should construct SDMs for ants, and what factors we should consider including in tropical or subtropical species.

My working hypotheses for the chapter are as followed: 1. Species distribution modelling can accurately predict potential occurrences of exotic Strumigenys species; 2. Distribution of exotic Strumigenys species are limited by soil microclimate rather than macroclimatic factors.

So far I am compiling occurrence records of exotic Strumigenys species from newly collected material, previous literature and any unpublished records from other studies, which will be the main data used in this study. Most literature records for ant specimens have already been compiled in the Global Ant Biodiversity Informatics Project (GABI; Guénard et al. 2017) which I will derive the literature record data from.

For each specimen I have noted down the specimen code, literature reference code (if present) taxonomic information, coordinates and source of the specimen (ongoing project or literature record) so other researchers can easily trace the origin of the specimen record (see example in Table 4):

TABLE 4 - Extract of exotic Strumigenys occurrence record dataset.
coll.code spec.code ref.code Genus Species Latitude Longitude Localname Adm2 Adm1 Country Source
NA NA GABI_02606224 Strumigenys emmae 18.77500 -88.43560 La Reserva Ecologica de San Felipe Bacalar se ubica a 15 km al NO de Bacalar entre los 1845’ de Latitud N y 8825’ de Longitud O. Direccion: 315. Distancia: 15030 NA Quintana Roo Mexico Rodriguez de Leon I. R., C. S. Venegas Barrera, G. G. Garcia, A. Azuara Dominguez, and M. Rosas Mejia. 2023. Ants of Mexico: Distribution and species richness in environments with varying levels of human impact. Biodivers Data J. 11: e109794.
ANTWEB1010138 NA GABI_02570157 Strumigenys emmae 50.36252 -4.74538 Rainforest Biome, Eden Project (indoor greenhouses), St. Austell NA South West England England Hamer M. T. and C. R. Turner. 2024. Strumigenys emmae (Emery, 1890) (Myrmicinae) new to Britain, with an updated key to the known Strumigenys of the West Palaearctic. Zootaxa
SB-P40-28 NA NA Strumigenys emmae 6.29616 116.72169 Kinabalu Park, Serinsim Substation NA Sabah Malaysia IBBL; 1000_Plots
SB-P54-01 NA NA Strumigenys emmae 6.30563 116.73038 Kinabalu Park, Serinsim Substation NA Sabah Malaysia IBBL; 1000_Plots

The dataset will be further cleaned up to remove duplicate records and enter any missing coordinates to ensure for accurate model predictions. If ultimately the coordinates of a species record could not be found they will be omitted and not be used to train the model.

For environmental variables I will extract data for macroclimatic variables from WorldClim and soil microclimatic variables from the Soil Temperature Project. To build the models I will select variables which previous literature have reported to be important in dictating the distribution of subterranean ants (also depending on the amount of data available for each variable). There was a PhD thesis by D.B. Booher (2017) who discussed on the patterns and abiotic factors that shape Strumigenys communities in the United States. In his study he selected mean annual temperature and precipitation at the driest quarter to be included in his models, as temperature and precipitation are major factors driving vegetation formations and prey (Collembola, as Strumigenys are mostly springtail specialists) abundance according to the author. I will consider including these as macroclimatic variables, and further select relevant soil microclimatic variables to compare against them. As Strumigenys are subterrannean ants, I am currently leaning towards soil temperature and soil humidity to include in the models.

This chapter is still developing so I have not yet began constructing the code to run the model. I have already discussed with another PhD student André Ibáñez about things to pay attention to when running and validating SDMs.

For the storage and management of data in this chapter:

  • Literature collection in Zotero will be exported as a RIS file and added as supplementary material during publication;
  • The dataset of exotic Strumigenys occurrence records is currently stored on my OneDrive with backup copies frequently uploaded to my USB. Datasets from this chapter will also be uploaded to the central lab drive and online data repositories such as Datahub as supplementary material during publication;
  • R-code for data cleaning and building SDMs will be uploaded to Github when the project has ended.

That is all I have at the moment. Curious to hear your thoughts :D