Trends in the homogenization of macromoth assemblages (2016-2023) in a Seoul City park

Abstract

As a Long-Term Ecological Network project in Korea, we conducted monthly macromoth sampling from May to October, 2016-2023, in Namsan Park, Seoul, at three permanent plots representing dominant tree communities: Quercus mongolica, Robinia pseudoacacia, and Pinus densiflora forests. Over eight years, we recorded 3,486 individuals from 283 species in 11 families. In total, 351 macromoth species from 13 families were documented in the city park, including 212 newly discovered species and 68 previously recorded species now disappearing. Species richness and abundance varied among the three forest types, with the Q. mongolica forest showing the highest values in both species and individuals. Overall species richness showed a nonsignificant decline, and auto regressive integrated moving average models predicted ongoing fluctuations in richness and a rising trend in abundance in the coming years. Macromoth assemblages in Namsan exhibited distinct clustering by forest type, with consistent distribution of body size groups emphasized throughout the study. Furthermore, relatively high faunal turnover within forests, combined with minimal annual variation, suggests a trend toward homogenization of macromoth assemblages across forest types. This pattern appears to be influenced by the city park's isolation, which may limit species dispersal and contribute to localized faunal differentiation.

Keywords: Diversity; Faunal change; Herbivores; Homogenization; Urban forest.

Fig. 1

Map showing the location of Namsan in central Seoul as well as the three forest types studied (Pd, Pinus densiflora tree community; Rp, Robinia pseudoacacia tree community; Qm, Quercus mongolica tree community). (A) Location of Seoul on the Korean Peninsula. (B) Location of Namsan within Seoul. (C) Locations of the three study forests in Namsan. Maps are based on Google Earth imagery (https://earth.google.com/), with additional graphic elements added using Adobe Photoshop CS7.

Fig. 2

Rarefaction and extrapolation curves of macromoth assemblages in Namsan, Seoul, Korea, using three Hill number orders (q = 0, 1, 2). Hill numbers equate to species richness (q = 0), Shannon diversity (q = 1), and Simpson diversity (q = 2). Pd: Pinus densiflora tree community; Rp: Robinia pseudoacacia tree community; Qm: Quercus mongolica tree community.

Fig. 3

Changes in macromoth (A) species richness (number of species) and (B) abundance (number of individuals) from 2016 to 2023 across three forest types in Namsan, Seoul, Korea. Pd: Pinus densiflora tree community; Rp: Robinia pseudoacacia tree community; Qm: Quercus mongolica tree community.

Fig. 4

Time series models of macromoth assemblages in Namsan, Seoul, Korea, from 2016 to 2023, with forecasts following for five years. (A) Species richness (number of species); (B) abundance (number of individuals).

Fig. 5

Trends in the proportion of macromoths by wingspan (small, medium, and large) from 2016 to 2023 in Namsan, Seoul, Korea.

Fig. 6

NMDS ordination of macromoth assemblages across the three forest types in Namsan, Seoul, Korea. P (Pd): Pinus densiflora tree community; R (Rp): Robinia pseudoacacia tree community; Q (Qm): Quercus mongolica tree community. Numbers after P, R, and Q indicate the sampling year.

Fig. 7

Average distance among macromoth assemblages across the three forest sites each year, based on NMDS ordination (Fig. 6) from 2016 to 2023 in Namsan, Seoul, Korea. Blue dots represent the dataset sites including all species; gray triangles show sites with > 5 individuals.