Diana M. Percy’s research while affiliated with University of British Columbia and other places

Hybrid cattail (Typha × glauca), a hybrid between native T. latifolia and introduced T. angustifolia, has been recently identified through macroscopic traits in the Fraser River Estuary (FRE), Canada. This detection represents a significant new focus of invasion for this taxon in North America. Typha × glauca has been referred to as a cryptic invasive species in the FRE due to its resemblance to other Typha taxa, and uncertainty around the reliability of identification based on field characters alone has slowed their detection and management. To test the accuracy of identifications based on morphology, we used molecular tools to evaluate 46 samples identified using morphology in the field as follows: 15 T. angustifolia, 15 T. × glauca, and 16 T. latifolia. Taxa were identified in the field across three populations. We used microsatellite markers and admixture analyses to verify our field identifications and found them to be 100% accurate. All 16 field-identified T. latifolia and 14 out of 15 T. angustifolia were pure genotypes. One T. angustifolia showed possible evidence of introgression. Eleven out of 15 T. × glauca were clear F1s, whereas three showed possible, but relatively weak, evidence of backcrossing and one may represent a potential F2. Hybrid samples displayed heterosis in three of the six traits measured, and strict intermediacy in the others, providing further evidence that most hybrids are F1s. This study assists in the regional monitoring and management of Typha by providing the first genetic evidence of T. × glauca in British Columbia, and a morphological method for “decrypting” this invasion within the FRE.

Stinging nettles (Urtica dioica) have a long history of association with human civilization, having been used as a source of textile fibers, food and medicine. Here, we present a chromosome-level, phased genome assembly for a diploid female clone of Urtica dioica from Romania. Using a combination of PacBio HiFi, Oxford Nanopore, and Illumina sequencing, as well as Hi-C long-range interaction data (using a novel Hi-C protocol presented here), we assembled two haplotypes of 574.9 Mbp (contig N50 = 10.9 Mbp, scaffold N50 = 44.0 Mbp) and 521.2 Mbp (contig N50 = 13.5 Mbp, scaffold N50 = 48.0 Mbp), with assembly BUSCO scores of 92.6% and 92.2%. We annotated 20,333 and 20,140 genes for each haplotype, covering over 90% of the complete BUSCO genes and including two copies of a gene putatively encoding the neurotoxic peptide urthionin, which could contribute to nettle’s characteristic sting. Despite its relatively small size, the nettle genome displays very high levels of repetitiveness, with transposable elements comprising more than 60% of the genome, as well as considerable structural variation. This genome assembly represents an important resource for the nettle community and will enable the investigation of the genetic basis of the many interesting characteristics of this species.

Even after decades of research on diversification in the Neotropics, our understanding of the evolutionary processes shaping Neotropical clades is still incomplete. In the current study, we used different divergence times and likelihood-based methods to investigate the influence of biogeography and host associations on the diversification of the most species-rich Neotropical psyllid genus Melanastera (Liviidae) using molecular phylogenetic data from seven gene fragments (four mitochondrial and three nuclear). The putatively monophyletic group of Neotropical Melanastera species has an estimated crown node age of 20.2 Ma (ML, CI 20.2-30.6) or 23.2 Ma (BI, 95% HPD 16.6-32.6), with diversification occurring mainly in the Upper Miocene, although some species groups diversified in the Pliocene and Pleistocene. Biogeographic analysis suggests that the Neotropical Melanastera originated from the Pacific region of South and Central America. We detected a shift in diversification rates that likely occurred either at the time of origin of Melanastera or during the main colonisation of the Atlantic and Amazon Forests, followed by a subsequent slowdown in speciation rates. State-dependent speciation and extinction models revealed a significant relationship between this diversification shift and the shift of Melanastera to the plant families Melastomataceae and Annonaceae, reflecting the impact of host switching on speciation rates in this group. This period also coincides with several independent dispersal events from the Atlantic and Amazon Forests to other parts of the Neotropics. Taken together, the results of the current study suggest that diversification of Melanastera was facilitated by major shifts to new host families, which may have promoted the dispersal of Melanastera into new adaptive zones with subsequent processes of local speciation.

Stinging nettles ( Urtica dioica ) have a long history of association with human civilization, having been used as a source of textile fibres, food and medicine. Here, we present a chromosome-level, phased genome assembly for a diploid female clone of Urtica dioica from Romania. Using a combination of PacBio HiFi, Oxford Nanopore and Illumina sequencing, and Hi-C long-range interaction data (using a novel Hi-C protocol presented here), we assembled two haplotypes of 574.9 Mbp (contig N50 = 10.9 Mbp, scaffold N50 = 44.0 Mbp) and 521.2 Mbp (contig N50 = 13.5 Mbp, scaffold N50 = 48.0 Mbp), with assembly BUSCO scores of 92.6% and 92.3%. We annotated 20,333 and 20,140 genes for each haplotype, covering over 90% of the complete BUSCO genes and including two copies of a gene putatively encoding the neurotoxic peptide urthionin, which could contribute to the characteristic sting of nettle. Despite its relatively small size, the nettle genome displays very high levels of repetitiveness, with transposable elements comprising more than 60% of the genome, as well as considerable structural variation. This genome assembly represents an important resource for the nettle community and will enable the investigation of the genetic basis of the many interesting characteristics of this species.

Insect herbivores frequently cospeciate with symbionts that enable them to survive on nutritionally unbalanced diets. While ancient symbiont gain and loss events have been pivotal for insect diversification and feeding niche specialization, evidence of recent events is scarce. We examine the recent loss of nutritional symbionts (in as little as 1 MY) in sap-feeding Pariaconus, an endemic Hawaiian insect genus that has undergone adaptive radiation, evolving various galling and free-living ecologies on a single host-plant species, Metrosideros polymorpha within the last ∼5 MY. Using 16S rRNA sequencing, we investigated the bacterial microbiomes of 19 Pariaconus species and identified distinct symbiont profiles associated with specific host-plant ecologies. Phylogenetic analyses and metagenomic reconstructions revealed significant differences in microbial diversity and functions among psyllids with different host-plant ecologies. Within a few millions of years, Pariaconus species convergently evolved the closed-gall habit twice. This shift to enclosed galls coincided with the loss of the Morganella-like symbiont that provides the essential amino acid arginine to free-living and open-gall sister species. After the Pariaconus lineage left Kauai and colonized younger islands, both open- and closed-gall species lost the Dickeya-like symbiont. This symbiont is crucial for synthesizing essential amino acids (phenylalanine, tyrosine, and lysine) as well as B vitamins in free-living species. The recurrent loss of these symbionts in galling species reinforces evidence that galls are nutrient sinks and, combined with the rapidity of the evolutionary timeline, highlights the dynamic role of insect–symbiont relationships during the diversification of feeding ecologies. We propose new Candidatus names for the novel Morganella-like and Dickeya-like symbionts.

The endemic Hawaiian mealybug genus Phyllococcus Ehrhorn (Hemiptera: Coccomorpha: Pseudococcidae) was erected in 1916 as a monotypic genus for a gall-inducing mealybug collected on the island of Oahu on Urera sandwicensis (now referred to genus Touchardia) (Urticaceae) in 1911. The species induces deep horn-shaped galls on the leaves of the host plant. Here we redescribe the adult female and adult male of Ph. oahuensis (Ehrhorn) and designate a lectotype; and we report a new record for Ph. oahuensis from the island of Maui. Additionally, we describe the adult female and second-and third-instar female nymphs of a new gall-inducing Phyllococcus species, Ph. cryptocaryae Percy, Watson & Hodgson, sp. n., found in galls on the leaves of Cryptocarya mannii (Lauraceae) in the central Waianae Mountains on Oahu. Also found galling the same host plant, and often in close proximity on the same leaf, were immatures of the triozid psyllid, Paurotriozana adaptata Caldwell, 1940 (Hemiptera: Psylloidea: Triozidae). Both the new mealybug and the triozid psyllid appear to be geographically restricted to the only remaining tree of C. mannii on Oahu and are therefore extremely vulnerable to extinction.

Carex dianae Steud. is an endemic sedge of St. Helena, an isolated island in the South Atlantic. Our study provides the first molecular sequence data for this taxon. We generated sequence data for plastid matK and trnK regions and nuclear internal transcribed spacer and external transcribed spacer regions to determine the placement of C. dianae in the broader Carex phylogeny. The placement of C. dianae falls within Carex sect. Spirostachyae Drejer, and it is sister to a clade including Carex clavata Thunb., Carex aethiopica Schkuhr (both from the Cape region of S. Africa), and Carex gunniana Boott (southern Australia). The existence of three divergent nucleotype groups and two plastotypes is revealed from genetic variation within C. dianae. The results suggest that the ancestor of C. dianae likely originated in the Cape region of South Africa, followed by transoceanic dispersal to St. Helena estimated at 4.4–4.9 million years ago, likely by a bird vector. The most divergent population is that on an isolated hill known as “The Barn”, which may represent a distinct taxon. The existence of highly structured molecular variation within an island only 16 km long is discussed.

A molecular survey of native and adventive psyllids in the central Macaronesian islands provides the first comprehensive phylogenetic assessment of the origins of the psyllid fauna of the Canary and Madeira archipelagos. We employ a maximum likelihood backbone constraint analysis to place the central Macaronesian taxa within the Psylloidea mitogenome phylogeny. The native psyllid fauna in these central Macaronesian islands results from an estimated 26 independent colonization events. Island host plants are predicted by host plants of continental relatives in nearly all cases and six plant genera have been colonized multiple times (Chamaecytisus, Convolvulus, Olea, Pistacia, Rhamnus, and Spartocytisus) from the continent. Post-colonization diversification varies from no further cladogenesis (18 events, represented by a single native taxon) to modest in situ diversification resulting in two to four native taxa and, surprisingly, given the diverse range of islands and habitats, only one substantial species radiation with more than four native species. Specificity to ancestral host plant genera or family is typically maintained during in situ diversification both within and among islands. Characterization of a recently discovered island radiation consisting of four species on Convolvulus floridus in the Canary Islands shows patterns and rates of diversification that reflect island topographic complexity and geological dynamism. Although modest in species diversity, this radiation is atypical in diversification on a single host plant species, but typical in the primary role of allopatry in the diversification process.