An artificial habitat increases the reproductive fitness of a range-shifting species within a newly colonized ecosystem

Zachary J Cannizzo,Blaine D Griffen,Bryan Benitez-Nelson,Susan Q Lang

doi:10.1038/s41598-019-56228-x

Abstract

When a range-shifting species colonizes an ecosystem it has not previously inhabited, it may experience suboptimal conditions that challenge its continued persistence and expansion. Some impacts may be partially mitigated by artificial habitat analogues: artificial habitats that more closely resemble a species’ historic ecosystem than the surrounding habitat. If conditions provided by such habitats increase reproductive success, they could be vital to the expansion and persistence of range-shifting species. We investigated the reproduction of the mangrove tree crab Aratus pisonii in its historic mangrove habitat, the suboptimal colonized salt marsh ecosystem, and on docks within the marsh, an artificial mangrove analogue. Crabs were assessed for offspring production and quality, as well as measures of maternal investment and egg quality. Aratus pisonii found on docks produced more eggs, more eggs per unit energy investment, and higher quality larvae than conspecifics in the surrounding salt marsh. Yet, crabs in the mangrove produced the highest quality larvae. Egg lipids suggest these different reproductive outcomes result from disparities in the quality of diet-driven maternal investments, particularly key fatty acids. This study suggests habitat analogues may increase the reproductive fitness of range-shifting species allowing more rapid expansion into, and better persistence in, colonized ecosystems.

Highlights

When a range-shifting species colonizes an ecosystem it has not previously inhabited, it may experience suboptimal conditions that challenge its continued persistence and expansion
We further explored the mechanisms behind any observed differences in reproductive potential by comparing five metrics between each of the three habitats: (1) the proportion of total body mass invested in reproduction; (2) egg energy content, which impacts larval quality[26]; (3) egg glycogen content, an important constituent of arthropod reproductive investment[27,28]; (4) egg lipids, the most important component of embryonic development[29]; and (5) the fatty acids (FA) that made up the egg lipids, which are critical to offspring quality and provide measures of the quality of both maternal reproductive investment and diet[30,31]
The smallest and average sizes of ovigerous females differed between habitats with salt marsh crabs becoming reproductively active at a smaller size than conspecifics in the dock and mangrove habitats while those from the dock were smaller than those from the mangrove

Summary

Introduction

When a range-shifting species colonizes an ecosystem it has not previously inhabited, it may experience suboptimal conditions that challenge its continued persistence and expansion. Pockets of favorable habitat that provide conditions which increase reproductive success within suboptimal novel ecosystems could play a key role in the fitness, persistence, and continued expansion of the population. These “analogous habitats”, so named because they act as ecological analogues to a historically-preferred habitat, are often artificial and provide improved conditions for organisms over www.nature.com/scientificreports a surrounding suboptimal environment8,14 [and references therein] These improved conditions could increase the quantity and quality of reproductive investment compared to the surrounding suboptimal habitat, leading analogous habitats to play an important role in the success of range-shifting species. The range expansion of the mangrove tree crab Aratus pisonii provides an opportunity to examine the reproductive impacts of a suboptimal colonized ecosystem (the saltmarsh), and an analogous habitat embedded within (boat docks), at the leading edge of this range expansion. Given the numerous benefits docks provide, they may increase the reproductive potential of A. pisonii over conspecifics elsewhere in the marsh, thereby playing an important role in the success and expansion of this range-shifting species

Methods

Results

Conclusion