I have the following Apex class and VF page.  Based on the selection of the tite, the corresponding role should display. I am using the actionSupport to pass the selected value onchange event, and assign the value to selectedTitle. But the selectedTitle is null everytime. Any ideas?

Apex class:
public class selectListController
{
    public String title { get; set; }
    public String role { get; set; }    
    public String selectedTitle { get; set; }        
    public List<selectOption> titleList { get; set; }
    public List<selectOption> roleList { get; set; }
    
    public selectListController()
    {
        titleList = new List<selectOption>();
        titleList.add(new SelectOption('', '--None--'));
        for (TitleRoleAssociation__c title : [Select Title_Definition__r.Name from TitleRoleAssociation__c]) {
            titleList.add(new selectOption(title.Title_Definition__r.Id, title.Title_Definition__r.Name));
        }
    }
    
    public PageReference getRoles(){
        roleList = new List<selectOption>();
        roleList.add(new SelectOption('', '--None--'));
        System.debug('Selected title: ' + selectedTitle);
        for (TitleRoleAssociation__c role : [Select Role_Definition__r.Name from TitleRoleAssociation__c where Title_Definition__r.Name = :selectedTitle]) {
            roleList.add(new selectOption(role.Role_Definition__r.Id, role.Role_Definition__r.Name));
        }
    
        return null;
    }
    
}

VF page:
<apex:page controller="selectListController">
    <apex:form>
        <apex:selectList value="{!title}" multiselect="false" size="1">
            <apex:selectOptions value="{!titleList}" />
            <apex:actionSupport event="onchange" action="{!getRoles}" reRender="role" status="status">                         
               <apex:param name="selectedTitle" value="{!title}" assignTo="{!selectedTitle}"/>
            </apex:actionSupport>            
        </apex:selectList>
        <apex:outputPanel id="role">
        <apex:selectList value="{!role}" multiselect="false" size="1">
            <apex:selectOptions value="{!roleList}" />
        </apex:selectList>        
        </apex:outputPanel>
    </apex:form>
</apex:page>