Patterns of Connectivity and Isolation in Marine Populations

<p>There is ongoing debate about the levels of connectivity among marine populations and despite its importance, there is limited information on the levels of population connectivity in most geographic locations. This lack of information severely limits our ability to adequately manage the marine environment including the design and implementation of Marine Reserve (MRs) networks. The specific objectives of this thesis were to: 1) Develop polymorphic microsatellite loci for my model species, the intertidal gastropod Austrolittorina cincta; 2) Conduct population genetic studies across A.cincta populations within the Cook strait region to asses the levels of connectivity within the regional marine reserve network; 3) Determine the levels of A. cincta larval movement and settlement from an isolated source; and 4) Asses the effect of the larval abundance on settlement rates. This thesis includes laboratory studies; population genetic studies; and field surveys within New Zealand and in the Wakatobi National Park, Indonesia. Eight novel polymorphic microsatellite loci were developed for A. cincta and five of these loci were used to investigate population connectivity across seven populations within the Cook Strait region, including four marine reserves. In the population genetics study, in contrast to what was expected, I recorded low, but significant genetic differentiation between most population pairs within the Cook Strait region, over a minimum and maximum spatial scale of 55 to 300 km, including several of the MRs. In a large-scale field settlement survey on the Kapiti coast combined with the use of microsatellite markers I investigated A. cincta larval movement and settlement and found that most larvae settle within 5 km, although some larvae might travel up to 50 km. Finally, the coral settlement studies in the Wakatobi National Park revealed lower coral settlement rates at sites with low adult coral cover, suggesting an effect of the the amount of local available larvae on coral settlement rates. While it has been suggested that marine populations are demographically open, with larvae connecting populations separated over large spatial scales, this thesis shows that populations might not be as open as previously considered and localized dispersal and self-recruitment processes might be a frequent feature in marine populations. This thesis provides valuable information to managers about marine reserve networks and the importance of adequate environmental protection to ensure future viable populations.</p>

Patterns of Connectivity and Isolation in Marine Populations

<p>There is ongoing debate about the levels of connectivity among marine populations and despite its importance, there is limited information on the levels of population connectivity in most geographic locations. This lack of information severely limits our ability to adequately manage the marine environment including the design and implementation of Marine Reserve (MRs) networks. The specific objectives of this thesis were to: 1) Develop polymorphic microsatellite loci for my model species, the intertidal gastropod Austrolittorina cincta; 2) Conduct population genetic studies across A.cincta populations within the Cook strait region to asses the levels of connectivity within the regional marine reserve network; 3) Determine the levels of A. cincta larval movement and settlement from an isolated source; and 4) Asses the effect of the larval abundance on settlement rates. This thesis includes laboratory studies; population genetic studies; and field surveys within New Zealand and in the Wakatobi National Park, Indonesia. Eight novel polymorphic microsatellite loci were developed for A. cincta and five of these loci were used to investigate population connectivity across seven populations within the Cook Strait region, including four marine reserves. In the population genetics study, in contrast to what was expected, I recorded low, but significant genetic differentiation between most population pairs within the Cook Strait region, over a minimum and maximum spatial scale of 55 to 300 km, including several of the MRs. In a large-scale field settlement survey on the Kapiti coast combined with the use of microsatellite markers I investigated A. cincta larval movement and settlement and found that most larvae settle within 5 km, although some larvae might travel up to 50 km. Finally, the coral settlement studies in the Wakatobi National Park revealed lower coral settlement rates at sites with low adult coral cover, suggesting an effect of the the amount of local available larvae on coral settlement rates. While it has been suggested that marine populations are demographically open, with larvae connecting populations separated over large spatial scales, this thesis shows that populations might not be as open as previously considered and localized dispersal and self-recruitment processes might be a frequent feature in marine populations. This thesis provides valuable information to managers about marine reserve networks and the importance of adequate environmental protection to ensure future viable populations.</p>

Pivot burrowing of scarab beetle (Trypoxylus dichotomus) larva

Many organisms live in the soil but only a little is known about their ecology especially movement style. Scarab beetle larvae do not have appendages to shovel soil and their trunk is thick compared to their body length. Hence, their movement through the soil is perplexing. Here, we established the observation and analysis system of larval movement and found that the last larval instars of Trypoxylus dichotomus burrow in two different ways, depending on the hardness of the soil. If the soil is soft, the larvae keep their body in a straight line and use longitudinal expansion and contraction; if the soil is hard, they flex and rotate their body. It is thought that the larvae adapt to diverse soil conditions using two different excavation methods. These results are important for understanding the soil ecology and pose a challenge to engineer of newer excavation technology.

Pivot burrowing of scarab beetle (Trypoxylus dichotomus) larva

Many organisms live in the soil but only a little is known about their ecology especially movement style. Scarab beetle larvae do not have appendages to shovel soil and their trunk is thick compared to their body length. Hence, their movement through the soil is perplexing. Here, we established the observation and analysis system of larval movement and found that the last larval instars of Trypoxylus dichotomus burrow in two different ways, depending on the hardness of the soil. If the soil is soft, the larvae keep their body in a straight line and use longitudinal expansion and contraction; if the soil is hard, they flex and rotate their body. It is thought that the larvae adapt to diverse soil conditions using two different excavation methods. These results are important for understanding the soil ecology and pose a challenge to engineer of newer excavation technology.

Baseline Plant-to-Plant Larval Movement of Spodoptera eridania in Bt and Non-Bt Soybean and Its Possible Impacts on IRM

The widespread use of transgenic technologies has led to the emergence of insect populations resistant to Bt toxins. Some lepidopteran pest species also appear to naturally have some level of tolerance to certain proteins, such as some species of Spodoptera to Cry1Ac. One of the main strategies to manage resistance is the use of refuge areas, the success of which is in part dependent on larval movement of the target pest. Thus, in order to assess the viability of a refuge strategy addressing Spodoptera eridania Stoll (Lepidoptera: Noctuidae) in Bt soybean, it was evaluated the larval movement across plants in Bt and non-Bt soybean, as well as the larval development and mortality on Bt and non-Bt soybean cultivars. We concluded that apparent S. eridania incomplete resistance resulting from high larval mortality and low adaptability on Bt plants, high larval dispersal, nondirectional larval movement, and random larval spatial dispersion suggest that structured refuge is more suitable than mixed refuge for managing resistance in S. eridania populations.

Impedance Measures and a Mounting Technique for Drosophila: Larval Movements, Heart Rate, Imaging, and Electrophysiology

Monitoring movements of larval Drosophila with electrical detection allows one to record the behaviors without the use of lights and cameras. This is a suitable technique when studying the use of light-sensitive proteins in optogenetic studies. Electrical measures are feasible to use in determining when a larva starts to move or continues to move after a light induced activation of channelrhodopsin. We have developed a technique using an electrical measure of the media as an index of larval movement. As a proof of concept, recordings with an infrared camera of the larval movement were simultaneous made with electrical measures. The two techniques parallel each other in their ability to index larval movements. Bright light-emitting diode (LED) lights used in optogenetic experiments tend to saturate the detectors of the camera unless filters are used and different filters maybe necessary depending on the LED spectrum and sensitivity of the camera. Impedance measures are independent of the type of LED or brightness. We also assessed the use of a non-solvent based glue (3M Vetbond) to hold larvae in place while measuring synaptic function of neuromuscular junctions, cardiac function and influence of modulators, or activation of light-sensitive channels.