Why so specious? The role of pollinators and symbionts in plant population structure and speciation along elevational gradients.

This thesis explores the role mutualist pollinators and their symbionts play in the genetic structuring and speciation of their host plants along an elevational gradient in Papua New Guinea. Using the fig and fig-wasp mutualism as a model system, we employed high-throughput sequencing techniques to explore fine-scale population genomics of both fig and wasps along their elevational range. We found there to be clear lowland and highland clustering of tree populations along the gradient, often with a mid-elevation contact zone. In the case of the pollinating wasps, we retrieved the same clustering except in this case, the genetic difference between clusters was high enough as to consider them as separate species. This result supports evidence from other studies challenging the cospeciation paradigm of one wasp species per fig species. In addition, we explore ecological traits which may promote, or at least, maintain, reproductive isolation between fig (sub)species along with behavioural preference tests from pollinating wasps. In order to further investigate the mechanisms promoting wasp speciation along the gradient, we describe Wolbachia infection status as well as strain type. Wolbachia-induced cytoplasmic incompatibility (CI) is often invoked as a possible speciation agent since it can rapidly provoke and maintain reproductive isolation between otherwise freely interbreeding insect populations. Finally, we explore non-pollinating fig wasp (NPFW) diversity along the gradient for a subset of our focal species. Our study reveals that there is a tight relationship between NPFW diversity and host species, and a mid-elevation peak

Are pollinators the agents of selection on flower colour and size in irises?

International audiencePlant–pollinator interactions are believed to play a major role in the evolution of floral traits. Flower colour and flower size are important for attracting pollinators, directly influencing reproduction, and thus expected to be under pollinator-mediated selection. Pollinator-mediated selection is also proposed to play a role in maintaining flower colour polymorphism within populations. However, pigment concentrations, and thus flower colour, are also under selective pressures independent of pollinators. We quantified phenotypic pollinator-mediated selection on flower colour and size in two colour polymorphic Iris species. Using female fitness, we estimated phenotypic selection on flower colour and size, and tested for pollinator-mediated selection by comparing selection gradients between flowers open to natural pollination and supplementary pollinated flowers. In both species, we found evidence for pollen limitation, which set the base for pollinator-mediated selection. In the colour dimorphic Iris lutescens, while pigment concentration and flower size were found to be under selection, this was independent of pollinators. For the polymorphic Iris pumila, pigment concentration is under selective pressure by pollinators, but only for one colour morph. Our results suggest that pollinators are not the main agents of selection on floral traits in these irises, as opposed to the accepted paradigm on floral evolution. This study provides an opposing example to the largely-accepted theory that pollinators are the major agent of selection on floral traits

Ficus hahliana Measurements

Width and height measurements for Ficus hahliana syconia from six sites along the Mt Wilhelm elevational gradient. Sample refers to the individual tree sampled and site refers to the collection site whilst elevation is given in meters above sea level. Width and height were are given in cm and volume is given in cm3. Tree sex is given where known

Genotype data for Ficus arfakensis

Genotype data for Ficus arfakensis, data for 8 microsatellite loci and 58 individuals with missing data coded as -9. The first column lists individuals and the second column lists the elevational site of each individual. Formatted for STRUCTURE

Ficus Transect Totals

Total abundance across all transects per elevation for a survey of species found growing along the Mount Wilhelm Elevational transect, updated in early 2016. Future taxonomic revisions can be expected, especially for species marked with asterix as these represent undescribed taxa (morpho-species names given)

Data from: Speciation in a keystone plant genus is driven by elevation: a case study in New Guinean Ficus

Much of the world's insect and plant biodiversity is found in tropical and subtropical ‘hotspots’, which often include long elevational gradients. These gradients may function as ‘diversity pumps’ and contribute to both regional and local species richness. Climactic conditions on such gradients often change rapidly along short vertical distances, and may result in local adaptation and high levels of population genetic structure in plants and insects. We investigated the population genetic structure of two species of Ficus (Moraceae) along a continuously forested elevational gradient in Papua New Guinea. This speciose plant genus is pollinated by tiny, species specific and highly co-evolved chalcid wasps (Agaonidae) and represented by at least 73 species at our study gradient. We present results from two species of Ficus sampled from six elevations between 200 m-2,700 m a.s.l. (almost the entire elevational range of the genus) and 10 polymorphic microsatellite loci. These results show that strong barriers to gene flow exist between 1,200 m and 1,700 m a.s.l. Whereas lowland populations are panmictic across distances over 70 km, montane populations can be disjunct over 4 km, despite continuous forest cover. We suggest that the limited gene flow between populations of these two species of montane Ficus maybe driven by environmental limitations on pollinator or seed dispersal in combination with local adaptation of Ficus populations. Such a mechanism may have wider implications for plant and pollinator speciation across long and continuously forested elevational gradientsif generalist insect pollinators and vertebrate seed dispersers also form populations based on elevation

Genotype Data for Ficus bernaysii and Ficus iodotricha

Genotype data for Ficus bernaysii (BER) and Ficus iodotricha (IOD), data for 8 microsatellite loci and four individuals per species with missing data coded as -9. The first column lists individuals and the second column lists the sampling site

Abundance, occurrence and time series: long-term monitoring of social insects in a tropical rainforest

The magnitude of worldwide insect decline is hotly debated, with multiple examples of stable or increasing insect populations. In addition, time series data for tropical insects are scarce, notably in rainforests where insect diversity is poorly known but reaches a peak. Despite social insects (ants, termites, bees and allies) being key organisms in these habitats, long-term monitoring data for these groups are crucially lacking. For many of these insects, the difficulty of locating nests in rainforests could be one reason. In this context, species occurrence in samples is often used as a surrogate for abundance to evaluate species distribution in space/time, but the loss of information is difficult to assess. In a tropical rainforest in Panama, we employed various sampling methods to examine the time series of seven insect assemblages with differing degrees of sociality: termite workers and soldiers, termite alates, bess beetles, litter ant workers, army ant alates, orchid bees, and nocturnal sweat bees. We used five community variables and six models related to occurrence and abundance, to test for significant trends in assemblages over a 13-year period (2009–2021). While assemblages of bess beetles increased, those of termite workers and soldiers, army ant alates, and orchid bees remained relatively stable. Termite alate, litter ant worker, and nocturnal bee assemblages showed signs of decline, demonstrating the need for monitoring distinct assemblages. Significant trends in generalized additive mixed models (GAMM) were observed in three out of five assemblages that could be tested. Our study indicates that trends in assemblages may be more informatively reported with abundance than with occurrence. We recommend (1) monitoring multiple insect assemblages as ecological indicators responsible for diverse ecosystem services; and (2) reporting species richness, changes in faunal composition, occurrence, and, when possible, using time-explicit analyses (such as GAMM models) for evaluating population trends over time

Abundance, occurrence and time series: long-term monitoring of social insects in a tropical rainforest

The magnitude of worldwide insect decline is hotly debated, with multiple examples of stable or increasing insect populations. In addition, time series data for tropical insects are scarce, notably in rainforests where insect diversity is poorly known but reaches a peak. Despite social insects (ants, termites, bees and allies) being key organisms in these habitats, long-term monitoring data for these groups are crucially lacking. For many of these insects, the difficulty of locating nests in rainforests could be one reason. In this context, species occurrence in samples is often used as a surrogate for abundance to evaluate species distribution in space/time, but the loss of information is difficult to assess. In a tropical rainforest in Panama, we employed various sampling methods to examine the time series of seven insect assemblages with differing degrees of sociality: termite workers and soldiers, termite alates, bess beetles, litter ant workers, army ant alates, orchid bees, and nocturnal sweat bees. We used five community variables and six models related to occurrence and abundance, to test for significant trends in assemblages over a 13-year period (2009–2021). While assemblages of bess beetles increased, those of termite workers and soldiers, army ant alates, and orchid bees remained relatively stable. Termite alate, litter ant worker, and nocturnal bee assemblages showed signs of decline, demonstrating the need for monitoring distinct assemblages. Significant trends in generalized additive mixed models (GAMM) were observed in three out of five assemblages that could be tested. Our study indicates that trends in assemblages may be more informatively reported with abundance than with occurrence. We recommend (1) monitoring multiple insect assemblages as ecological indicators responsible for diverse ecosystem services; and (2) reporting species richness, changes in faunal composition, occurrence, and, when possible, using time-explicit analyses (such as GAMM models) for evaluating population trends over time