The Song Laboratory of Insect Systematics and Evolution

With more than 28,950 extant species, Orthoptera are the most diverse order among the polyneopteran insect lineages. The order includes familiar singing insects, such as crickets and katydids, as well as often‐devastating pests, such as grasshoppers and locusts. Orthopteran insects have diversified into numerous lineages that occupy every conceivable terrestrial habitat outside the polar regions and play integral roles in their ecosystems. Such diversity in form and function has attracted researchers who use these insects as model systems for studying anatomy, bioacoustics, chemical ecology, evolutionary ecology, life‐history traits, neurobiology, physiology, and speciation.

Nevertheless, there has been an alarming rate of decline in taxonomic expertise in Orthoptera in the last 30 years and currently there are only a handful of experts in the world who can adequately describe and classify these insects. Due to this contemporary lack of taxonomic expertise, many groups within Orthoptera need modern taxonomic treatments. My lab currently represents the only orthopteran systematics lab in the U.S. that can train the next generation of orthopterists. Thus, I feel an urgent sense of mission to advance and revitalize the field of orthopteran systematics, and my lab aims to become the world-renowned center for advancing orthopteran systematics.

My research program on orthopteran systematics is quite broad, covering descriptive and revisionary taxonomy, morphological and molecular phylogenetics, of various lineages within Orthoptera. Although my own taxonomic expertise is in grasshoppers (Acrididae), my research program has no boundary when it comes to taxonomic scope within Orthoptera.

Since 2008, my research program has been focusing on clarifying phylogenetic relationships of major orthopteran lineages, which have produced novel phylogenetic hypotheses for Orthoptera, Acrididae, Tettigoniidae, and Pyrgomorphidae. Most of these studies have used morphology and Sanger sequencing data, but over the past few years, I have developed a new tool set that can generate phylogenomic data (over 1,000 loci) from any orthopteran taxa. The use of this new tool opens up a new possibility to producing robust and comprehensive phylogenetic hypotheses, which can serve as important reference points for understanding the evolution of interesting and agriculturally relevant traits of orthopteran insects. Through extensive fieldwork and collaboration, I have already accumulated a very large collection of DNA-grade specimens. Using these, and additional specimens from future collecting expeditions, I will produce new and robust phylogenetic hypotheses for several major orthopteran clades over the next five years.

Recently, I received a large 5-year NSF-NERC grant (DEB-1937815) in collaboration with Fernando Montealegre-Z, Nathan Bailey, Seunggwan Shin, and Michael Whiting that aims at building a robust phylogeny of Ensifera (crickets, katydids, and relatives) based on 1,600 taxa and 1,000 loci using phylogenomics. This project uses hybridization-based target enrichment probes for phylogenomic data generation, and will generate a large amount of transcriptome data, as well as biomechanics data to understand the evolution of acoustic communication. In addition, I also have ongoing projects on reconstructing the phylogenies of the South African Lentulidae, Jerusalem crickets (Stenopelmatidae), and band-wing grasshoppers (Oedipodinae), which will rely on a similar data generation technique. The resulting phylogenetic studies will be used to test previous taxonomic classification schemes as well as to study the evolution of ecologically interesting and agriculturally relevant traits in various orthopteran groups.

Representative Papers:

Locusts are grasshoppers belonging to the family Acrididae that can form dense migrating swarms through an extreme form of density-dependent phenotypic plasticity. In nature, depending on local population density, locusts are polyphenic along the continuum between two extreme phenotypes, commonly known as solitarious and gregarious phases, and this ability to respond to density is called locust phase polyphenism. Locusts respond to increased population density by changing color, behavior, life history traits, physiology, biochemistry, and gene expression patterns. Locust phase polyphenism is considered one of nature's most amazing examples of coordinated phenotypic plasticity.

Source: Bizarre Beasts: The Strange Thing That Turns Grasshoppers Into Locusts

The grasshopper genus Schistocerca is an ideal system to study how locust phase polyphenism has evolved because it contains both the swarming locust and non-swarming grasshopper species. Using this genus as a model system, I have established a robust research program aiming at understanding how density-dependent phenotypic plasticity has evolved in a comparative framework using both laboratory and field-based manipulative experiments. This work has been supported by NSF CAREER Award (IOS-1253493) and TAMU-CONACYT grant.

For the next five years (2020-2025), I will focus on unraveling the molecular mechanism of locust phase polyphenism using genomics, transcriptomes, epigenetics, and reverse genetics on several locust and grasshopper species in Schistocerca. Especially, the availability of the desert locust (Schistocerca gregaria), the Central American locust (Schistocerca piceifrons), and the South American locust (Schistocerca cancellata) as well as other non-swarming species as laboratory colonies allows ample opportunities to carry out various manipulative studies. This work is largely funded by the NSF Biology Integration Institute grant (DBI-2021795). These data will provide important insights into the evolution of locust phase polyphenism, which could lead to deeper understanding of how locusts swarm and potentially develop a better method of controlling these pests.

Representative Papers:

Among animals with internal fertilization, many species have species-specific male genitalia with morphological divergence among closely related species that is often dramatic and complex. This pattern is especially evident in insects, and male genitalia are considered one of the most important and useful species-diagnostic characters in insect systematics. Recent theoretical developments in genital evolution show that male genitalia are under sexual selection and evolve very rapidly.

My research on the evolution of male genitalia has focused on understanding functional morphology in a comparative framework and I have been promoting the idea that male genitalia are complex organs consisting of several functionally different components that might be under different selective pressures and developmental constraints. Recently, I have begun exploring the use of new imaging technologies (such as micro computer tomography [μ-CT]) to study the functional morphology of male genitalia in unprecedented details using the grasshopper genus Melanoplus, which is known to have highly divergent male genitalia among species. As we understand more about the functions of different genital components, we will be able to tease apart the processes shaping the evolution of these fascinating traits. My ultimate goal in this line of research is to connect functional morphology with genomics in a phylogenetic framework to understand the evolution of one of the most important morphological traits in insect systematics.

Representative Papers:

Now is the age of very large molecular data in systematics. However, our ability to analyze large and complex molecular data is severely outpaced by our ability to generate such data. My research aims at bridging this gap in the context of mitochondrial genomics. Mitochondrial genomes (mtgenomes) are the smallest extant organellar genome, which in insects encode for 13 protein-coding, 22 tRNA and 2 rRNA genes with an average size about 15,000 bp. It is now technically feasible to sequence the mtgenome of a given organism in its entirety within a short period of time. The complexity of the genome structure and the large yet manageable size of the genome make mitochondrial genomics an ideal model system for exploring various challenges of today’s molecular systematics.

As a postdoctoral research fellow of an NSF-funded AToL Beetle Tree of Life Project, I generated complete mtgenome sequences for 72 key beetle species and I am conducting a similar research on Orthoptera as well. I was involved in developing a bioinformatics tool that can aid genome annotation and data management [MOSAS].

The availability of mtgenomes from diverse lineages within a given taxonomic group allowed me to study genome evolution in a comparative context. My research has focused on the evolution of genome structures, atypical stop codons, transfer RNAs, and lineage-specific gene rearrangements in a phylogenetic framework. I am also interested in determining how best to analyze mtgenome data as a phylogenetic marker for deep-level relationships. So far, I have shown that mtgenome data are often highly affected by the past molecular events, resulting in patterns such as among-site rate variation and base compositional heterogeneity and that incorrect phylogenetic inference is inevitable when such systematic bias is not accounted for. I am currently exploring various ways to overcome systematic bias in phylogenetic reconstruction.

Representative Papers:

Nuclear mitochondrial pseudogenes (numts) are non-functional copies of mtDNA in the nuclear genome, which have been found in major clades of eukaryotic organisms. Among insects, Orthoptera, especially grasshoppers, are known to have exceptionally high numbers of numts, making them an ideal model system for studying numts. I have shown that numts can be easily coamplified with mtDNA using PCR-based methods, that numt coamplification can compromise the effectiveness of DNA barcoding and mitochondrial systematics, that numts are extremely abundant across major lineages of Orthoptera, and that numts can be effectively used as molecular fossils in recently diverged lineages. This line of research stemmed from my own struggle with generating mitochondrial sequences from grasshoppers, which has serendipitously transformed into an exciting area of research. There are still numerous questions to be addressed because the molecular mechanisms driving the nuclear integration of mtDNA, and maintenance and transmission of numts are still largely unknown. This line of research fits well within the field of molecular systematics and I find it fascinating in terms of molecular evolution. I intend to continue and expand this research program in the future.

Representative Papers: