Small size does not restrain frugivory and seed dispersal across the evolutionary radiation of Galapagos lava lizards

Frugivory in lizards is often assumed to be constrained by body size;only large individuals are considered capable of consuming fruits, with the potential of acting as seed dispersers. However, only one previous study has tested the correlation of frugivory with body and head size at an archipelago scale across closely related species. All nine lava lizards (Microlophus spp.) were studied on the eleven largest Galapagos islands from 2010 to 2016 to investigate whether frugivory is related to body and head size. We also tested whether fruit abunda nee in flue nces fruit con sumption and explored the effect of seed ingestion on seedling emergence time and percentage. Our results showed that across islands, lava lizards varied considerably in size (64-102 mm in mean snoutvent length) and level of frugivory (1-23%, i.e., percentage of droppings with seeds). However, level of frugivory was only weakly affected by size as fruit consumption was also common among small lizards. Lava lizards consumed fruits throughout the year and factors other than fruit abundance may be more importa nt drivers of fruit selecti on (e.g., fruit size, energy con tent of pulp). From 2,530 droppings, 1,714 seeds of at least 61 plant species were identified, 76% of the species being native to the Galapagos. Most seeds (91%) showed no external structural damage. Seedling emergence time (44 versus 118 days) and percentage (20% versus 12%) were enhanced for lizardingested seeds compared to control (uningested) fruits. De-pulping by lizards (i.e., removal of pulp with potential germi nation inhibitors) might in crease the chances that at least some seeds find suitable recruitment conditi ons. We con eluded that lizards are importa nt seed dispersers throughout the year and across the whole archipelago, regardless of body size.

Potential role of lava lizards as pollinators across the Galápagos Islands

Lizards have been reported as important pollinators on several oceanic islands.Here we evaluate the potential role of Galápagos lava lizards(Microlophus spp.)as pollinators across their radiation.Over 3 years,we sampled pollen transport by 9 lava lizard species on the 10 islands where they are present,including 7 single-island endemics.Overall,only 25 of 296 individuals sampled(8.4%)transported pollen of 10 plant species,the most common being Prosopis juliflora,Exodeconus miersii,Sesuvium sp.and Cordia leucophlyctis.At least 8 of these plant species were native,and none were confirmed as introduced to the archipelago.Despite the low overall proportion of individuals carrying pollen,this was observed in 7 of the nine lizard species,and on 8 of the ten main islands(Española,Fernandina,Floreana,Isabela,Marchena,Pinta,Santa Cruz and Santiago),suggesting that this is a widespread interaction.The results reported here support the potential role of lava lizards as pollinators across their radiation,although they may represent a relatively modest contribution when compared with birds and insects.However,we cannot discard that lizards may be ecologically significant for particular plant species and ecosystems given the specific climatic condition and functional diversity of each island.

Frugivory and seed dispersal in the Galápagos:what is the state of the art?

The Galápagos are considered a model oceanic archipelago,with unique flora and fauna currently threatened by alien invasive species.Seed dispersal is an important ecosystem function with consequences for plant population dynamics and vegetation structure.Hence,understanding the seed dispersal abilities of the assemblages of frugivores will inform scientists and managers of the dynamics of plant invasions and improve management planning.Here we provide the first comprehensive review of published information on frugivory and animal seed dispersal in the Galápagos.We collected data from a variety of sources,including notes of the first naturalist expeditions,gray literature available only in Galápagos collections,and peer-reviewed journal articles.Plant–animal frugivorous interactions were retrieved from 43 studies and compiled into an interaction matrix describing 366 unique interactions.Most studies focused on fruit consumption as a driving force for natural selection,but seed fate was seldom considered.Although most(71%)of the interactions involved native plants,more than one-quarter(28%)involved introduced species.Interactions involving birds are considerably more common than those of reptiles and mammals,probably reflecting a research bias towards birds.Despite the historical importance of the archipelago as the laboratory for evolutionary and ecological research,understanding of its seed dispersal systems is limited.We end the review by suggesting 3 priority areas of research on frugivory and seed dispersal in the Galápagos:(i)target research to close knowledge gaps;(ii)the use of a network approach to frame seed dispersal at the community level;and(iii)evaluation of the effect of seed dispersal as a selective pressure acting upon plants and frugivores.Finally,the output of this research has to be properly delivered to the Galápagos National Park Services to help increase management effectiveness.

Galápagos land iguana(Conolophus subcristatus)as a seed disperser

The role of the most common land iguana(Conolophus subcristatus)in the Galápagos Islands as an effective seed disperser is explored in this study.A total of 5705 seeds of 32 plant species were identified from 160 scats,4545 of which(80%)appeared visually undamaged.Germination trials of 849 seeds from 29 species revealed that at least 10 species remained viable after passing through the iguana’s gut,although only a small propor­tion of those seeds(4%)germinated.In any case,we argue that C.subcristatus exerts an important role on the 7 Galapagos islands where it occurs because of its abundance and capacity to ingest and disperse seeds at long distances.Our results strongly suggest that the Galápagos C.subcristatus plays an important role as a seed dis­perser of not only of native species but also some introduced plants in the Galápagos Islands.

Lack of support for Rensch＇s rule in an intraspecific test using red flour beetle （Tribo/ium castaneum） populations

Rensch＇s rule proposes a universal allometric scaling phenomenon across species where sexual size dimorphism （SSD） has evolved： in taxa with male-biased dimorphism, degree of SSD should increase with overall body size, and in taxa with female-biased dimorphism, degree of SSD should decrease with increasing average body size. Rensch＇s rule appears to hold widely across taxa where SSD is male-biased, but not consistently when SSD is female-biased. Furthermore, studies addressing this question within species are rare, so it remains unclear whether this rule applies at the intraspecific level. We assess body size and SSD within Tribolium castaneum （Herbst）, a species where females are larger than males, using 21 populations derived from separate locations across the world, and maintained in isolated laboratory culture for at least 20 years. Body size, and hence SSD patterns, are highly susceptible to variations in temperature, diet quality and other environmental factors. Crucially, here we nullify interference of such confounds as all populations were maintained under identical conditions （similar densities, standard diet and exposed to identical temperature, relative humidity and photoperiod）. We measured thirty beetles of each sex for all populations, and found body size variation across populations, and （as expected） female-biased SSD in all populations. We test whether Rensch＇s rule holds for our populations, but find isometry, i.e. no allometry for SSD. Our results thus show that Rensch＇s rule does not hold across populations within this species. Our intraspecific test matches previous interspecific studies showing that Rensch＇s rule fails in species with female-biased SSD.