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The center-periphery hypothesis (CPH) predicts that peripheral populations will have lower genetic variation than those at the center of a species' distribution. However, ecological margins do not always coincide with geographical edges when topographies are diverse. Historical climate changes can also strongly affect genetic variation. Here, we examined genetic variation in Phyllodiaptomus tunguidus, a calanoid copepod endemic to the north-eastern Oriental. This species was predicted to exhibit a complex pattern of genetic variation across its range due to the diverse topographies and stable climate history of the north-eastern Oriental. To test this, we used geographic distance to the center of the distribution, current ecological suitability, and climate during the last glacial maximum as geographical, ecological, and historical factors, respectively, in our analyses. We measured genetic diversity and population differentiation using mitochondrial and nuclear markers. This showed that P. tunguidus had 3 refugia during the last glacial maximum (LGM). Such a pattern of multiple refugia complicates the determination of the center and periphery of spatial genetic diversity. Both regression models and redundancy analyses failed to support the CPH. Instead, they showed that geographical, ecological, and historical factors together shaped population genetic structure in this species. Ecological factors explained significantly more genetic variation than did geographical and historical factors-however, all three factors interacted significantly to affect the pattern of genetic variation. The results extend our understanding of the CPH and the extent to which it can explain genetic variation across populations., (© The Author(s) 2022. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE). All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

We conducted a preliminary analysis on the effects of various physical and chemical parameters on the morphometry and reproductive capacity of the calanoid copepod Filipinodiaptomus insulanus (Wright, 1928), endemic to the Philippines, by proxying clutch size (CS). Specimens and water quality readings were obtained between October 2019 and February 2020 from four sites in northern Philippines. Only the sizes of adult males and non-ovigerous adult females showed significant differences (P < 0.05) among populations. Non-eutrophic, temporary shallow waters were the predominant habitat type of F. insulanus , corroborating earlier observations that it is mainly found in relatively pristine environments. Correlation analysis showed a significant indirect relationship (P < 0.001) between the size of individuals and temperature, a potential adaptive response to its environment. Such observations may be valuable in preventing the disappearance of this species from parts of its previously known range. [ABSTRACT FROM AUTHOR]

The presence of the invasive calanoid copepod Arctodiaptomus dorsalis in Philippine inland waters has been reported in numerous studies. Attempts to understand how it effectively proliferated in the country's freshwaters have shown its preference towards shallow and productive waters - a feature shared by most lakes in the Philippines. In this study, we compared the body size and reproductive capacity - proxied by clutch size (CS) - of ovigerous female A. dorsalis obtained from established populations in the seven maar lakes (SML) of San Pablo, Laguna, Philippines. These measurements were also correlated with selected water quality parameters. Collection of ovigerous A. dorsalis and water quality parameters were conducted on a 3-mo sampling period during the southwest monsoon season in 2016. Statistical analysis shows that there exists a significant difference between the prosome length (PL) and CS of A. dorsalis from the seven lakes (p < 0.001), with the shallowest and most productive lake containing the most fecund population. Additionally, all water quality parameters showed a positive correlation with the PL and CS of ovigerous A. dorsalis from the SML (p < 0.01). This shows that the SML provides favorable conditions for the propagation of A. dorsalis, making it a model for in situ investigation of this invasive species' ecology; the first step in incorporating zooplankton ecology as a tool for the development of lake management systems. [ABSTRACT FROM AUTHOR]

The article discusses findings of a study on the composition and quantity of zooplankton found in freshwater sardine that were caught in Taal Lake, Philippines. The research revealed that 90 percent of the stomach contents of freshwater sardine consisted of large adult copepods and 10 percent cladocerans and rotifers. An analysis of collected samples from July 2003 to July 2004 to determine the zooplankton diet of Sardinella tawilis determined that freshwater sardine prefers to consume larger prey since they are more visible. Researchers noted that smaller-bodied organisms dominated the zooplankton community because of size-selective predation.

• Individual-based model to study the production of an invasive copepod. • Model integrates the effect of food concentration on several individual endpoints. • Calibration of the model benefits from measures obtained in vivo. • Quantify the combined impact of food and predation on egg and offspring production. Arctodiaptomus dorsalis is an invasive calanoid copepod originally from America and has recently established a population in Lake Taal in the Philippines. It has been proposed that eutrophication due to aquaculture contributes to the establishment and success of this species. This study aimed to clarify this hypothesis by quantifying the effect of increasing food concentration on the reproduction of A. dorsalis using an Individual-Based Model. We parameterized food concentration-dependent equations to simulate the effect of different food concentration on the reproductive traits (latency time, embryonic development time, clutch size, and hatching success) of this species using data from the literature and simulated the reproduction of 1000 independent females for 20 days at different food concentration, taking into account the variability among individuals. The simulation results showed that the cumulative production of eggs and offspring increased continuously with time when the food concentration was above 3.2 × 104 cells mL−1, suggesting that this value was the threshold concentration required for stable reproduction of A. dorsalis. This value is not particularly low compared to other copepods. Hence, our result revealed that the food use efficiency of A. dorsalis is not particularly outstanding and urge the need of a comparison with native species to confirm a possible superiority. We suggest that A. dorsalis has filled the ecological niche left vacant by the disappearance of the original species due to the deterioration of water quality caused by the eutrophication of the lake. The reproductive cycle model developed in this study constitutes a necessary step in the development of a complete population dynamics model, which can help clarify the invasive abilities of A. dorsalis. [Display omitted] [ABSTRACT FROM AUTHOR]

Despite the increasing interest in studying Cladocera and Copepoda in Philippine freshwaters, there is a need to update our knowledge on its taxonomy and distribution in highly urbanized areas, such as Metropolitan Manila. This paper presents an updated listing of freshwater microcrustaceans and their distribution in Metropolitan Manila, considering the continued deterioration of water quality and increased urbanization in many areas since the last comprehensive study on these taxa in 1950s. We collected water samples from 33 freshwater sites in Metropolitan Manila and 23 of which were found to contain microcrustacean zooplankton. A total of 13 species were identified including two new locality records for C. cornuta and D. dubium in Pasig River. All 8 cladocerans, we identified have already recorded in previous studies while 3 cyclopoid copepods are new records for Metropolitan Manila. Furthermore, 16% of all known freshwater microcrustacean zooplankton species in the Philippines are found in Metropolitan Manila, including the Luzon-endemic Filipinodiaptomus insulanus collected from man-made reservoirs in less-disturbed habitats (an urban wildlife park, golf course and eco-park). Other identified species such as Thermocyclops taihokuensis may serve as indicator for high levels of nutrient. These results point to the importance of monitoring urban aquatic biodiversity for their potential in determining aquatic ecosystem health and of maintaining urban aquatic sanctuaries which may serve as alternative habitat for flora and fauna in rapidly developing urban centers such as Metropolitan Manila. [ABSTRACT FROM AUTHOR]